Well TBH most of the time i leave when there is no more money left. But only in small sums like 20$ or so if i go over 100 i cash half and play half.
What's the use of doing this I'm sure the next day you again gamble with those same funds you saved yesterday and do the same thing and finally after few days you lose everything, you do know it's better to stop gambling if you are not getting any profit otherwise eventually you are going to lose the funds you are trying to save one day or another