"slip-up" is a simple error or mistake. "move on" means you should stop thinking about the something and carry on/continue with whatever you were doing! "Learn from your slip-up and move on" means "learn from your mistake and continue with your life/don't dwell on your mistake too much" Another use of these phrases could be: "Move on, it was only a slip-up!" "The relationship is over, you need to move on" "I slipped-up this morning when I was spelling a really easy word!"

It means: If your blood sugar is high because of simply eating too much, learn from your mistake and continue with your life after you have dealt successfully with a bad experience/mistake. In other words: slip-up = a mistake, often accidental. "Move on" has a number of meanings, but in this case it means "to start to continue with your life after you have dealt successfully with a bad experience"