Built a fintech-ish startup all by myself, zero funding. I didn't intend to do it all by myself but it's not a sexy business so no one was jumping to go full-time. It came close to breaking me as a human being, honestly.

Anyway, I went from being a CTO who was constantly being pitched horrible no-good business ideas by first times CEOs - who as a rule, wanted to give me 10% equity but also wanted me to build the project for free - to a CEO who closed countless sales and knows his CAC and LTV like the back of his hand.

If I can, so can you but you have to manage CAC:LTV.