annoys me and freaks me out that it was all psychological.

It's not really psychological. There's a lot of physiological processes involved. One you have to go from a sugar burning metabolism to a fat burning metabolism. That can be troublesome for people, during that transition electrolytes can get out of balance.

If you want to try fasting again, I recommend starting a ketogenic diet first, get comfortable with keto, get past the adaptation phase after 2 or 3 weeks. Increase your electrolyte consumption the entire time. Salt, potassium, magnesium. Then, try a fast and see if you feel different, make sure you continue your electrolytes supplementation.

Once you're in ketosis, starting a fast usually isn't much trouble for people, they don't really notice it.