Being diagnosed with extreme MTHFR, getting on a high dose of methylfolate and the correct meds.
Went from having daily, very heavy brain fog to zero. Thought for years I was just lazy and stupid. Doing simple things left me more mentally exhausted than others, and I just thought everyone felt like I did, but were better at pushing through it.
Turns out, not lazy or stupid at all.
Went back to school, got my AA and into a field desperate to hire. Doubled my salary.