As the other commenter mentioned, cognitive psychology is well-developed (working memory, the relationship between action impulses and our subjective awareness thereof, etc). And there is very good social psychological research on a number of useful topics including diffusion of responsibility, the fundamental attribution error, the effect of dissenting voices on groupthink, the influence of perceived authority on human decision-making (Milgram), etc. Kahneman and Tversky's contributions (and all of "behavioral economics") could also be considered social psychology.

Anyways, though, I'm not sure it's super useful to "believe with conviction" in science. Shouldn't we hold all results up to scrutiny, and weigh them on the evidence?

Along these lines, by far the most important takeaway from the last 50 years of academic psychology, imho, is that we are usually far too willing to trust our own personal judgment. The brain is as much a self-deception engine as it is a reasoning machine. We have a far hazier view of what actually goes on in our minds than we usually think we do.

Cognitive psychology topics such as memory and reading have a strong paradigm, and established results. In general, their effects are much easier to replicate because you require far fewer participants. This is because you can validly make multiple observations of the same participant.