I will die on this hill: you simply cannot be a great founder and great investor at the same time.
The way you think about everything in life as a great investor is orthogonal to being a great founder.
You don’t have an unbiased objective view of the world as a founder.
SO: 'i lost all my money in stock market and got fired'
me: 'i thought u were up a bajillion percent'
SO: 'yeah but im now moving back to mom's basement'
me: 'well i haven't given myself a salary yet'
SO: 'yeah i know, u should leave me u deserve better'
me: 'we will figure it out. i will work overtime. i will give myself a tiny salary for now. i won't let u go homeless'
SO: 'oh by the way that was all a joke. im not fired and i made a bajillion percent returns again'
me: *hangs up and gets back to work*
now im actually going to slap him