1. There’s always another day, another chance. You have your whole life to live and interact with people and try again. Getting rejected that time means nothing. “You can be the tastiest peach in the world and there will still be someone who hates peaches.”
2. What do you get if you don’t ask?
The same thing you get if you are rejected.
3. If you really like them, wouldn’t you want them to be happy? It’s better to let people live their lives and you yourself go find someone who appreciates you for you, not someone who won’t be happy with you and end up having a seriously bad relationship.