I can relate to this. I was briefly around 1800 in HD and DE, but found that if I didn't play for a while that I'd come back and find myself outclassed. I uninstalled and reinstalled the game about five times over a couple of years because I found myself putting too much time into it to try to maintain a competitive skill level.

I actually tried to get into chess after quitting AoE2, to fill that strategic urge, but found the same thing - if I wasn't dedicating time and thought to it regularly I couldn't retain the advances I'd made in skill without going through a "warm up" period all over again (usually of losses).