The best way I learnt to play rock-like was playing way out of BR. Because that is bad, here's an idea:
Set aside 50$. Play 50NL, just one table. Imagine that this was ALL your money. While this will not make you as much money as possible, it WILL teach you to be goddamned disciplined and you'll only be playing top hands, thus very few hands. Don't worry if you lose them due to badbeats, but if you DO lose them, consider how you played, consider whether you were more disciplined or not.
Do this either until you lose those 50$ or until you turn them into 150 or (if you manage that quickly) until you feel you're disciplined enough preflop to actually give the REAL game a try and play 10NL properly bankrolled.
Hell, it was a great exercise for me.

Either that, OR pick up a hands chart and swear by it. You'll drop it eventually, but at the start only play the TOP hands there, no exceptions, no "hmmm this KTo looks good against a raise".

After solving the preflop problem, you'll be more disciplined postflop as well, because you'll get used to discipline in poker. From there on, it's just practice practice practice.
And post hands on the forum. and use the converter when you do.
And good luck.