I'm not sure if I'm a good example, but after I got divorced, my self esteem was in the pits. My ex had always told me I was stupid, didn't know anything and never would, etc. So I didn't feel "good enough" for anyone. But it wasn't long after the final divorce decree that I met someone and my heart started fluttering!

I was REALLY interested in this guy, but didn't have enough self-esteem to even THINK he could be interested in me. If wasn't too long tho before he showed interest too, and lo and behold we started dating. While I had some insecurities and fears, I tried to keep a handle on them. We dated for several years, and finally got married!!
So just try not to let your insecurities get the better of you. If you think you're a good partner, then you probably ARE.

DON'T even think about past relationships because they have nothing to do with this one -- your new partner is a completely different person than your other one. So this relationship is totally different.

Don't compare it to the other one.
I hope you two work out. If you don't, it's no disaster. It's just a learning experience. God bless and please take care. Hugs, Lee