Hey there, Ravenshade.
Reading this whole post... how to word it? Let's just say I often had similar thoughts, of not exactly the same.
Why keep trying when you keep being betrayed? Or people don't believe you? Or whatever seems to be the case, people either 'leave' you/let you be or don't seem to trust you.
Am I getting close?
When, however, I feel happy/neutral, there is one stronger thought: To keep on trying.
Because, to me, that is what life is about. To keep on trying. Even if in the end one gets hurt in some manner, the moments that you do feel happy, are so worth it. At the time you're happy, etc. This are moments to strive for. Not to give up on. Even if it feels it happens every single time that you 'fail' or 'lose' in some way. Don't give up.
In the end, Nick opened up to Judy. There is two ways to look at his quote. The first one you already mentioned. Another one is what I like to hold on to the most: When bad stuff happens, I indeed don't show it gets to me. If I happen to be able to talk to someone about it, I'll surely do. Otherwise I keep to myself. But when good stuff happens, in general, I just enjoy it. I usually don't show ecstasy or the like from the start, I build it up.
And I also try to remember I do have friends. Online and offline. Friends, acquaintances, etc. I usually help my friends, but in turn if I have a problem, I can go to them. (This is also what separates my real friends from any fake friends I might come across. Real friends will stay by you if you have a problem, fake ones pretend they want to listen to your problems, but then actually just decide to leave or complain about the problems you're having. That is, taking into account, if you're not down/having a problem 24/7 whenever you meet up with your friends or other people. No one wants to be around a depressed person the whole time, afterall.)
Maybe I've written too much, and the like. I feel I haven't really gotten to the point. My main point is to not stop trying. I know it sounds cliché, but a lot of cliché's are there for a reason.
Either way, I hope in some way this helps.
Take care, Ravenshade.