Nice Guy

So ladies lets talk! Is being a nice guy worth it? I just got out of a three year relationship and she is the one that broke it off. She still comes by all the time she wants to hang out with me and i still do stuff for her all the time. She still shows no respect for me for all the things i do. I dont want to fall back down for her and i try not to but i cave. She textes me and she ask me to help her out and i say to my self “NO” But i cave and run to her aid. I am just a nice guy like that. Even tho she steped on my heart and left me i still cave for her. Is being a nice guy even worth it! Should i just turn into a jerk and treat people shady. Hey! It works for most guys! Or in the end will being a nice guy get me the girl of my dreams! Comment on the folks in need of help.