People learn fast. It is a well known effect of a traumatic experience that cannot be escaped (e.g. rape): dissociation. A person escapes inside their head because they cannot escape physically. Is an abusive childhood a traumatic experience that cannot be escaped? Hell yes!
Yes, people learn fast. Having a childhood "dissociation training" can teach someone very well to do it almost constantly. It's addictive. It removes stress instantly - of course it is addictive. I read some blog posts about people dissociating "almost all the time" and I was imagining some half dead zombies and thinking "wow that must be tough". Until recently. Until I realised that I constantly do it too.
Know that feeling when you're on your way to the shop and suddenly you find yourself in front of your apartment door? Or hearing only the first and the last word of something that someone was just telling you? Spacing out at work during the meetings? Not remembering what you did today or yesterday? Well, maybe because indeed you were not mentally present there.
It's a defence mechanism. As with all such mechanisms it is important to ask (now DBT style):
  • what was it defending me from in the past?
  • do I still need to defend myself from those things today?
  • what tradeoffs do I have to make today in order to maintain this mechanism?
  • is it worth it?
The answer here is simple - no it is not worth it. It is not worth not to live your life.