Fights with Girlfriend

She's the first official girlfriend I've had, me at age forty-three. I've tried before with other gals but have always been rejected before we reached the exclusivity stage. Things with this gal have been stormy, especially since exclusivity. A lot of it's my own fault, my own indecisiveness and anxiousness about the relationship, which I'm frustrated by. I really want things to work, so why do I keep sabotaging it?