Do you ever question what your doing?

I could be so sure that this is what I want to do and how I want to do it, and this is what I want in the future, then once I think about everything that has happened and what's been done, can it all be undone? Can you really let go of the pain that's is eating you in the inside and change your plans like that? because you want to just for you and not the other person? How do you determine what you're doing is right?