Unless you've already established that 1k hands is your perfected length of session, then start playing with your session size a little bit. Try playing a single table 50-hand session. Then try a two-table 200-hand session. The fact is that you have to concentrate on every hand as if it your only hand of the session.

If you are habitually spending the first 200 hands of every session "getting used" to solid poker, then you are sacrificing EV on these hands. Instead, spend this time away from the tables putting your head into the correct playing mindset. Review some hands, browse 2+2, observe a table before you sit, etc.

On top of all this, you likely have a small sample size and selective memory regarding this issue. I've heard you can download a program called tilt-blocker that prevents you from seeing your stack size at the table. Another option is to always buy in for random amounts, making it harder for you to recognize whether you are up or down, or to continue adding chips to the table until you are no longer sure of how much you are up or down.

My "standard" buy-in at 1-2 is $60, but sometimes I'll buy in for $42, or $67, or $80. Sometimes when I drop below $60, I'll top off with another $32. This seems to work for me.