I don't know about motivation but when I see an opportunity for work, I just go for it. I'd rather be doing something rather than sitting idle.
When I started out, it was to stop taking money from my parents because they're poor. I was homeless for a short while so I slept in the cybercafe at night since I had the keys. I lived on one or two egg puffs a day that my friends bought for me. I had nowhere to go to take a bath so I'd just a take wet-wipe "bath" with a towel. People used to make fun of me about how dirty I am but I was completely helpless. Eventually I got a home for 5k a month and I took it knowing very well that I don't make enough to afford that so I had to keep looking for new things to do to afford the bare minimum for food and shelter. I was late on paying rent almost every month but I managed to get by.
I think it was after YouTube when I discovered new things and my pace of learning accelerated.
Now I'm doing okay but I still have naysayers who tell me I don't have a "real" job. Couldn't care less.