You have no idea what you can or cannot do until you try. I spent my youth pushing and shoving and I have a pretty good idea of where I stand when it comes to the types of girls I should be gaming, the types of guys to just back down from, and the types of guys to push back.
I found late last year that I had some weight to lose, so I smacked myself for even letting myself get so out of shape, and lost 15 lbs in 2 months and kept it off (and then another 5 after that).
I used to subscribe to the idea of a friends ladder and a 'good' ladder, and that they were separate entities once it was established; or at least not worth worrying about. Earlier this year, on autopilot, I approached a friend and even though it was more complicated than I'd prefer (I think there's a DJ discussion thread where I verified something), I was able to do a successful 'ladder jump'. All without excessive planning, tricks, and what not. Just me and her, kino escalation, isolation and close. Terminology for ideas that are as obvious as they were natural to me.
Recently I met a friend of my brother's gf. She interested me, so I built up rapport over a few parties (complications with location prevented isolation) and when the time presented itself I did what needed to be done.
Looking back over the last half year, the only thing that I learned is that the only thing stopping you from doing anything is the actual act of doing -- are you doing it, or are you thinking of doing it? This is the basis of ideas like 3 second rule: the 3 seconds has nothing to do with anything except to stop you from double thinking and doubting. You do it. You don't even consider you might be rejected.
If I had one tip, it would be 'don't think: just do' (and then evaluate after you are out of the situation).
For you personally, you are 39 and thinking of improving. If your life is in order, the only thing left to do is to go through the DJ Bible.