First day the average line was -151, so it's not surprising there were more wins than losses. More than likely this will fall on deaf ears, but when evaluating something in a small sample size, line movement is way way waaaaaaay more important than wins and losses.
Say you are trying out two kinds of systems in the NBA. One goes 30-20 but on average does not beat the close, and the other goes 20-30 and beats the close by an average of 1 point per game, focus more on the one that is 20-30 so far. If someone is consistently beating the close, that is a better predictor of how they will do going forward.
Even on the first day you tried this, 10 of the 15 games either didn't move in your direction, or moved away from you.
Unfortunately there is no easy way to win in sports betting. The bottom line is you beat the close, you win.