What was your longest fast? Instead of aiming for 5 days, maybe try to beat your personal record each time. Because if you’ve already done X hours, then you know you can do it and X + additional hours isn’t too far off.
I’m currently on day 5 of 7 and this is the longest I have fasted. I usually eat one meal a day, so day 1 was easy for me. Days 2 & 3 are where the willpower comes into play. Think about why you are doing it! Days 4 & 5 are much easier. I have mental clarity, almost no anxiety and I’m so determined and proud of myself. If I can do it, anybody can.