Alan, you have to think of the big picture. No matter when you start or quit you will get dealt random cards at the same frequencies. You won't get dealt two-pair or 3oak or any of the better hands any more often just because you choose a time to quit. As a result you will see the same choices that anyone else sees and you will receive the same frequency of hits on the draw. Over time these will average out just like anyone else.
In order for you to do better than the optimal return you need to get a higher frequency of good deals or good draws. However, there's nothing that makes that happen. Every hand is independent. For example, think about tossing a fair coin. Do you think there's any way for you to assure more than 50% heads? Does it matter when you toss the coin? If you get a few heads up will it matter if you stop then and start again the next day?
PS. I win around 45% of my sessions. I could increase that number with small win goals and big loss limits but it would not affect my overall results. I would just lose more money when I do lose to make up for the higher number of wins. This is similar to how Singer's system works. Yes, you win more sessions but the big losses bring you back to normal expectation.