This is a massive topic that I could spend ages on but I'll just say a few things. First off, go watch Actualised.org's video on how we stop ourselves from being happy. It's an insanely interesting that fundamentally explores parts of our brain and our minds that we ourselves never dare venture. The general premise is that if I asked you if you wanted to be happy, chances are you'd say 'of course!'. Then if I asked you if you wanted to be happy all the time, no matter what, just unconditional happiness, you'd also be like 'yes!'. But if you really want unconditional happiness, that doesn't mean everything suddenly goes your way- Because it won't. You don't control the entire world, you don't control what goes on around you. You cannot control anyone or anything, it's all an illusion. So to be happy all the time, that means you have to surrender the idea of everything going your way because it never will. It means that no matter what happens, you are happy. You get beaten up? You're still happy. You get cheated on? Still happy. Your family dies in a fire? Still happy.
See? Unconditional happiness isn't what you think it is. It's something much more complex and difficult. Your current state of happiness works with reward and punishment. Something 'good' happens? A feeling of happiness. Something 'bad' happens? A feeling of sadness. The truth is nothing in this world that happens is good or bad, how we perceive it is what makes us feel the emotion. Personally, I perceive everything as good because the bad stuff allows me to grow as a person which is super important.
So anyway, watch the video on YouTube because Leo explains it much better than I do, but I think it's a very very important life lesson we should all pay attention to and work on self actualisation.