He loves me; He loves me not

I was cleaning out my emails this week, and one of the starred (important) ones was as follows from SI's mistress:

Good morning. I know it’s ridiculous that I’m writing again already but I didn’t sleep at all and I realized something, which I wanted to share: SI loves you more. He wants a real life with you, not with me. I realized this when I was thinking about the timing of everything. He told me about you in July, I guess in the hopes that I’d just pack it in and go. And even after that, he still never really told you about me until you did some “research” and confronted him. He never intended to screw things up between the two of you; I guess it was my fault for not slinking off with my tail between my legs.So anyway, that’s what I’m going to do now. If you guys want to be together, I really do wish you every happiness. I won’t get in the way and I won’t be in his life. I sent him an email late last night, saying basically the same thing. I don’t want this drama in my life, and we all deserve to be happy at the end of the day.That’s all. I just thought you would want to know

This was about 5 years (October 14th).  Obviously SI's power of seduction worked because this did not happen - she was wrong (and in fact it became even less civil later), he won her over and she moved in; but you can see WHY I kept thinking it would work out. 

As I am making HUGE changes right now...ones I am not sure if I have thought all the way through and ones that scare me a little, how can I not think back to the chaos that has drifted my life in this direction?  Because of that, I feel like everything I do now is unsure. I have a horrible feeling I keep making the wrong decsions.  And even 5 years later, my life is no more 'settled' than it was during this chaos and I am still just as unsure about everything.

I want nothing more to rewind the last 5 years and start over...maybe 7 years.  I probably would not have settled down in my current area. If I knew when I left things were DONE DONE, I would have quit my job and moved away for a while, instead of floating by waiting for things to fix itself.

I am about to make a decision that will greatly affect me...and I have a hard time thinking about the long term consequences of it because I hate to think in the long term I'd still be single, at a job I don't like, not afford to live alone, etc.

Very confused right now. Not sure how to make the decision...flip a coin?