for me it never worked the pattern you mention, because it’s really difficult to stop something you are doing or learning and start something else with the same focus.
What I used to do, and I do now as much as I can, is to test and when you are totally lost or without ideas continue learning. You are going to get tired of looking for vulnerabilities, so that’s the time you take to learn new things (even if you don’t understand them!), and then the desire to find vulnerabilities comes back. That’s the way it works for me. However, I’m not sure everyone’s mind works the same way so maybe you should start trying different ways to balance learning and working (looking for vulnerabilities in this case) and eventually you are going to figure out the best way for you to get results.
I hope it helps.