<human>: Condense the text into a few key points

-I [30/m] am currently in a serious and very happy relationship with a female who is about my age.  We are not yet engaged but actively and openly talking about engagement and our future together.  I love her and hope to be her husband one day.

-*but* I have a past, as many of us do.  I was hurt by a girl in the past and throughout my twenties I used my charisma and looks to get back at her through all the other girls in the world.  I fancied myself a playboy and bedded quite a few women.  I've since realized how stupid that is BUT I still have a lot of tendencies from that time.  

-My struggle now is that I find myself acting in this way without thinking.  The event which triggered this post just happened an hour ago.  I was staying late to help a relatively new co-worker [27/F] finish a project at work.  She and I are friendly and I've definitely noticed her checking me out.  I admit, I haven't let her know I have a girlfriend yet.  Also, I was a bit buzzed as I was already working late and had 2-3 glasses of whiskey (acceptable in my office after about 9pm and she had a glass as well).

-Long story short, I offered to drive her home since it was late, ended up in her apartment for a nightcap and was on her sofa with her right up next to me.  I could sense the tension in the air and thankfully I had a moment of clarity and realized I was about the sacrifice a future with the woman of my dreams for a night with a co-worker.  BUT what scares me is that all the little steps that brought me to that sofa felt a bit like auto-pilot because I've done these exact 'moves' with dozens of girls before.
<bot>: I used to be a womanizing d-bag.  I love my girlfriend but I find myself automatically flirting with anything with breasts.