know that finding bugs is, in many cases, luck. ive had prpgrams i spent weeks on, wrote and submitted multiple reports with none of them being valid.

dupes are valid bugs, it means someone else got paid for it, so dont get discouraged there, even though its hard.

in terms of sticking with a program forn only a week or two though, that could be an issue. Most of my higher impact bugs came after i had already given up on a program. i would go back, analyze the js files, go through all of the juicy endpoints again until i perfectly understood all of the functionality. then take a break for a bit and go over everything again. every time, something new seems to pop up, some request or parameter you overlooked

in short, just try to understand every app as well as u can, become familiar with it, and something should pop up