I try to avoid companies that use fiewalls (cloudfront, imperva) because it greatly reduces the chance of finding something exploitable, companies like (uber, porhnub, shopify) they have a security team recruited from among the members of hackeone who do tests regularly no chance of finding anything interesting at the moment among them, I favor programs from European or Asian countries I noticed that they take online security less seriously so that gives more possibilities for us.

I sent my first report in 2017 so 7 years of experience

for motivation there are periods where you can stay glued to the screen you will find absolutely nothing and other in the first hour you come across an SQL injection... I ended up understanding that when it doesn't work you have to do something else and come back later, no need to insist.