To add to other answers, following is what i believe are the benefits:-

1. Makes you tough and you adapt to situations where you have to be happy even when things dont go your way. :- When in one-sided love, you would love other person to do things you do for them. But when things like Seen but no reply; Online but no Hi as mentioned by Palak happens, you feel disappointed. But believe me every time you become more stronger mentally or at least you should. You learn to overcome situations where results dont go your way.
2. Makes you a better person.:- You wont discard/ignore anyone else just like the other person did to you. You learn the importance of other’s feelings making you a good human being. This is the best part since everyone wants to be listened to/thought about in their lives.
3. Learning about life.:- You won’t get everything you want in this world. The only control you have on someone is what you have to offer to them and not the reverse. Its a see-saw wherein happiness and sadness are playing on opposite sides. You have to try your level best but the results are not in your hands. Give but don’t expect anything in return.
4. Maturity.:- You become forgiving as you understand humans are bound to making mistakes. Its not about being superior like the other person tries to be or to portray someone inferior. Everyone is and must be treated equally important.