You learn very young what makes you happy, and what does not. That distinction lays the groundwork for the kind of human being each child is going to turn out to be. It is important that children learn to assert themselves whenever they find themselves in a situation that makes them uncomfortable. That discomfort could be the pain visited upon those who are close to them, it could be an older person trying to teach them something other than the truth. Children are intuitive. All of them. They understand the truth.
Your happiness should be a thing that you nurture. It is precious. It is also important – once you have discovered what makes you feel happy – that you understand whether your kind of happy is a healthy happy or not. There are many unhealthy happies out there and they can be destructive, but they each have their reason for being. When we can see their cause(s) then we can decide whether or not we wish to keep them, whether or not they are necessary to carry as baggage. Sometimes the unhealthy happies are simply happy happies trying to explain an inexplicable pain. For some things there are no words.
When you love truly, unconditionally, the happiness of the other is as important as your own. When you understand that happiness feeds off itself, then you will understand that putting the other’s happiness ahead of your own is not only the supreme act of self-sacrifice, it is the natural thing to do when you find yourself at cross-purposes. It’s like finally getting for yourself something you have dreamed of your entire life and then giving it away for no good reason. Who on this planet would do that?