OT: Overcoming the Gambler's Mindset

I used to play a lot of blackjack. While I knew the odds were stacked against me, I was always very good about winning a few units and walking away. I knew I could beat the odds in the short run and would take my winnings and run. When I made the transition to poker, I found myself doing the same. Because the two games are so different, I know I need to adjust my "walk-away" threshholds. After some thinking, I had the following questions that I was hoping to get some insight on.

When you are playing sngs, 20+ a day, what do you look at when making your decision to start up another set or to call it a day? Are you looking at +/- for the session, do you shoot for a number (20 a day) and re-evaluate whether you should play more once you hit the number?

I find that I often start slow and come on strong to finish up for the day. For example, this is not uncommon for me. I started 0/6 the other day, but finished 1, 8, 2, 2, 3, 1. If you start slow and come on strong, would you continue to play because you are making good decisions and your hands appear to be holding up? Or, if you hit your 20 that day, ended strong and were up 6 buy ins, would you walk away for the night?

In terms of losing, do you set a daily loss limit? Lets say you are 8 sngs into your 20/day target and you are down 8 buy ins. Do you call it a day and have at it tomorrow, or do you power through the 20 and see where you stand when the dust clears?

Your thoughts would be appreciated.