I wouldn't describe myself as a successful
grinder yet but here is what I do.
-I play 6 tables and just open them all up at once, each takes different time for BB to come around so that somewhat prevents instant bombardment of decisions. I tend to play slightly more cautiously near the start of the session and avoid any marginal spots until I have an idea of villains and table dynamics.
-I try not to let winning or losing a big pot affect subsequent decisions, it's not easy sometimes but it get easier the more you play.
-I don't find myself involved in 2 big pots at the same time very often. When in a big pot I take my time, not by counting or anything but by slowing down on the turn and river giving me time to think things through. I do this even if I make my decision quickly to avoid giving off timing tells