Happiness is a matter of definition. Problem is, people who are not happy measure it by the 'ups' of momentary happy excitement (a surprise party given in your honor, giving birth, getting married, winning the lotto, etc) which are just a piece of a happy life but which could also be part of an 'unhappy life'. Nobody can live in a constant state of euphoria, our bodies could not take it. Happiness, in my personal opinion, is liking yourself EXACTLY as you are, knowing that your life is worth it, that you are contributing (in whichever way this might be) to a better world, that, even if there are drawbacks, you can overcome them, that you have people to love and who love you in return, etc. It's the daily contentment of a life well lived and it's also doing what you like to do. Does everybody have this? No. Can everybody achieve it? Yes, under normal circumstances. People that live in a war zone, have no food, live in pain, see their relatives killed like flies and don't perceive a light at the end of the tunnel obviously cannot but it doesn't mean that circumstances will not change or that anybody living a 'regular' life could not get it if they set their mind to it. Because been 'happy' all the time is nothing but a state of mind and something we need to work on all the time. It's found inside yourself and entirely up to you to get to that point. Of course that sometimes we get grumpy, angry, disgusted, disappointed, etc but that doesn't mean we don't have a happy life. These are just the 'lows' that compensate for the 'highs' I mentioned before. If there was no lows, we would not appreciate the highs as much as we should. But even during the lows, we can look into ourselves and KNOW we have a happy life.
I have nothing in my past that depresses me. My first and second husbands were no good and I had to start with no family to help me (they were all back home), no job, no home, no money, in a strange country with a language that was not my first or even my second, and nothing but two suitcases three times in my life (and the third time I had a 3 year old child) and there were times when it was hard to keep on going but I did. I got a job, an apartment, I went to college at night, etc and I even had to live for many years without dogs which was pretty hard on me (I had birds and cats but no dogs). I had cancer and had to have surgery and radiation treatment, three of my children were 'difficult' (and that's an understatement when it comes to my middle daughter), I lost my house in Pennsylvania to foreclosure and had to admit that I simply could not continue doing animal rescue full time, etc. etc. Poop happens. It's part of life. But I've never done anything knowing it was the wrong thing to do and every set-back has been an excellent learning experience which ended up making my life richer and better (yes, bad husbands included). And, because I've gone through real hard times and overcame them, I've learned that there is absolutely nothing to be anxious about the future because I know for a fact that, regardless of how hopeless the situation might look, I will bounce back.
As to parrots and their plight in captivity... as with anything that depends on human beings, some have better lives than others but thinking that we are the ONLY ones that can provide them with good treatment is not realistic and quite arrogant if you think about it. My birds live cage-free in a room fitted just for them, have other birds for company and a number of them have mates, they eat a fresh food, organic diet made from scratch, are kept at a solar schedule and have good quality full spectrum lights, branches for perches, etc. etc but, even though my life revolves around their needs, I worry all the time and I am constantly looking for ways to improve their lot, I don't fool myself into thinking that I am the only one that can do this or that nobody can do it better because I know for a fact that there are better situations for them and I am not talking about been released to the wild, I am talking about fabulous sanctuaries like The Oasis, Foster Parrots or Best Friends where parrots live in flocks, have outdoor aviaries, etc.
One should never compare one's husbandry to worse ones... my husband does this all the time and it always aggravates me: "People keep them in cages" - "People just put out commercial food for them" - "People don't worry about the sun going down" and, my favorite: "People have normal lives"

But I don't care how other people do it. I never compare my husbandry to other people's, I compare my parrots lives to the way Nature meant their lives to be. That's my bar. Needless to say, my husbandry is waaaay below Mother Nature's but I keep on trying and my birds lives have improved tremendously over the years. I also used to keep them in cages in human areas, to a human light schedule, give them bad food, etc. but I've learned and I've changed their living conditions. And I will continue to change and hopefully improve them even more.
The important thing is never to look at a pet parrot's life and say: "It's the best it has ever been" but instead say "It's not as good as it should be" - and never to put our feelings for them before their wellbeing. That and nothing else was what drove people to trap them and breed them to be used as human pets. It's selfish, it's self-centered, and it's plain wrong. I have in the past and will, most likely, rehome some of them in the future if I think that what I can offer them is not enough. Because loving them to pieces is not what makes the difference. Love does not trump all. One has to think of what's best for them and nothing else. And, yes, they do miss us at the beginning but they learn to love their new owners as much or more than they love us. We might be the center of their existence while they live with us but, give them a better situation and they will happily adjust to it.
And yes, toolove, parrots are heartbroken when the breeders steal their babies. Of course, one cannot 'see' inside an animal's brain but, then, we can't see inside another person's brain, either. We go by their actions and reactions, don't we? Well, it's the same with animals (and this is what Bekoff's work is mostly about). I've seen an OWA male stand close to his mate, a RLA female, which couldn't stand straight due to her handicap so she could lean her bad side on him (and he knew which side was her 'bad' one and went around to it to make it easy on her). And he did it all night long as well as for hours and hours and hours during the day. And I've seen a female GCC protect her mate, a peach fronted conure severely handicapped, and defend him from a larger bird even though this is usually what males do for their females. I might not be able to see inside their brain but I know these birds love their mates and not only don't abandon them when they are sick or hurt but actually figure out what they need and do it for them. As to them been heartbroken when their babies are taken... let me tell you a true story: a couple that bred macaws did not believe that their birds actually care that much when they heard it at a lecture so they put a camera inside their nest to see how they reacted to it and when the film showed them (mainly the mother but the father, too) scratching the material aside desperately looking for the babies and crying all night long the first night, and the mother refusing to leave the nest for two days, they were convinced and not only stopped breeding them but actually went around showing the film to other people. These are intelligent animals that love deeply, mourn the passing of their loved ones, can count and figure things out, do you really believe that they would not know that their babies have been stolen or that they would not feel the loss?