Do not play based on profit
There's probably two equally good ways to play cash game sessions:
1. Hours -- Kinda like a part time job, you set your hours and play more of less within them.
2. Hands -- This isn't as rigid, because sometimes you might be forced to play more than normal because your number of hands is lower than normal.
Again, don't be like "Okay, I'm going to win 3 buy-ins a day, I'll play until I hit that everyday", because that's a nightmare.