The best way I know to tackle placebo, is to make sure your life involves some kind of repeated routine deep concentrated work or activity. Get into a good schedule of doing something every day (or at least attempt to). E.g. work full time or play guitar 2 hrs a day, 5 days a week. Then you can test medication / supplements, and compare the weeks of concentrated work (or ability to concentrate / go deep in what you are doing / thrive at work) to other weeks of concentrated work. This is what helps me not placebo. Whereas if I take some kind of supplement, but I am kind of lounging around, getting bored, unconcentrated, not really working hard or putting my mind towards something, it is very easy to become agitated, overthink/overanalyse, subtly paranoid, or biasedly optimistic (placebo) about something I've ingested (supplement, food, etc).
At least attempt to concentrate, and make it a strong attempt. As we all know, POIS can really damage your concentration, but if a solution is working and is not placebo, your ability to concentrate is improving, consistently, this should be a good sign something is working and thus unlikely to be placebo.