Throughout life, you are going to face rejection and disappointment. But your mental attitude towards that must be like a car's windshield wiper. As soon as they happen, learn from them and wipe them away. Do not dwell.
The moment you find someone who is on the same wavelength as you, drop all pretence and make your advance. That is a once-in-a-lifetime opportunity. 99.9% of people will never make that connection. If it happens to you and you act cool and let it slip away, you are a fool.