I would have studied basic tactics more as well as doing more analysis on my own games. I've found the way to improve quickest for me is to see the major mistakes I made in my own games and trying to think of a better move. Going over GM games may be good but a lot of the time the ideas may be too abstract and complex meaning its hard to really apply that knowledge to your own chess games.
I'm quite interested in your comment that some titled players hate chess yet carry on playing. Surely if you 'hate' it you would just quit?? Even if they are addicted it's not as if they are physical dependant on chess or that it is essential as it's just a hooby right? It just seems it bit lame to say 'I hate chess but I'm so addicted I can't stop playing'.
If you could go back, about the way you first studied chess, what you tried to learn first; then found out later something would have been better to study first.
What would you have decided differently?
If you could..would you have even gotten into chess? I know some titled players that hate chess with a passion, but can't stop playing.
Maybe you feel the same way?