Every living thing deserves happiness, IMO. Real, lasting happiness is not possible, though, until you can learn to treat other living things as you would like to be treated. It's amazing what shedding your negativity can do. Most people who are depressed, unhappy, angry, etc wear those emotions like a cloak, because at first glance it seems easier to pass it off to others or bask in it than it is to fix it. But trust me, when you can cast it aside and spread love around to everything you encounter, it will be returned to you, and happiness can be achieved.
In other words, your happiness is not the responsiblity of, nor the result of, anyone else. It comes from you and way you interact with the rest of the world.
Some people may do that, but those who are truly happy will try to help anyone who isn't or at least will do what they can in passing. I've found, like I said above, that the key to being happy is to bring happiness to others. This is why I post in TDS a lot, even though I'm a very happy person. When I was insecure about my happiness 6 months to a year ago, I avoided TDS like the plague because it would bring me down every time I read it. But now I attempt to give advice based on my experiences, and instead, it makes me feel so good and joyful to have helped someone.
Spread the love, spread the love. It's true that all you need is love.