Walk away, or try harder?

"One of the hardest parts of life is deciding whether to walk away, or try harder?"

Brain says walk away. Heart says try harder.

Is it always like that?

I want things with him to work out so badly I can feel it all slipping out of my control. Fight or flight? I guess it is just a matter of determining what I am willing to risk. 

Should I dive head first into dark waters?

Brain says walk away. Heart says... go for it.