One of the things to keep in mind with respect to "trust in [one's] thought processes" is that INFPs and INTPs share a tertiary Si, which has some rather odd effects, in particular the effect of making it difficult to "unlearn" bad information. In INTPs, this shows up when, no matter how much evidence one presents, the evidence is rejected when it contradicts "known facts" (Si). Part of the problem is that it doesn't matter that the known facts are wrong, because it takes a lot of work to rebuild the mental framework. It's a very trustworthy framework, and changing to a new one takes a lot of time and effort, therefore, such individuals tend to force others to prove that it's worth their time and effort. In INFPs, it isn't a structure of facts and data and logic, but of feelings and impressions and understandings. For both INTPs and INFPs, these structures are intrinsic, and not very far from one's sense of identity.
INxJs can be stubborn cusses, but interestingly don't seem to have this problem. If new facts (Te, Fe, Se) appear that contradict assumptions, then the INxJ "troubleshoots" the assumptions, looks for the key item that is "incorrect" (which can be hard to put into words, because other people cannot see our thought flows), and fix it. This is how I troubleshoot software on a daily basis: I don't assume it's correct, I assume that it demonstrably works pretty good, but might contain functional flaws. I think it's the "functional" bit that doesn't jibe with INxP thought patterns. It's more "is" than "functional". Undoing "is" means changing things intrinsically, while undoing "functional" is just a matter of substituting in a corrected process.
I think for INFPs, the answer is to "listen closely" to oneself, and listen for sounds and echoes that indicate that something "isn't right". Don't stop listening, because it's the listening (Fi, believe it or not) that will hear where the Si-crystal is fractured, and if you hear it long enough, then it will convince you that it's wrong, and let you know where the problem lies. Then make whatever adjustment seems correct, and then continue listening: you might have missed something, or even made something worse. INTPs need to do something similar, but I would label it "internal thinking" (what else?!), where they're thinking over their own logical patterns, looking for Si faults.
Just remember that "listening" is a key Fi strength, just as being able to instantly synthesize data into an integrated understanding is an Ni strength.
Unlikely
