Disappointment is just the distance between expectation and reality. So either expect less and accept the reality Or expect more and turn it into reality.
If you love someone, but your someone loves someone, you be the same someone like before, because time’ll come that your someone will realise, that you are not just someone, but you are the one.
Do not only be close with someone who makes you happy. Be close with someone who cannot be happy without you. It makes a lot difference to him at least.