Anything to do with "you're not succeeding because you feel/believe a certain way" while true, is utterly unhelpful. "Turn off your thoughts and feelings dude and you will be a master PUA!" THANKS SENSEI.

Being serious though, let's analyze one example. "Have abundance mentality." Okay, so where does abundance mentality come from? It doesn't come from anyone telling you there are plenty of fish in the sea. Deep-seated abundance mentality comes from actually being desired by an abundance of people. So if John Doe asks why he can't get girls to like him and you say "it's simple chief, you're missing abundance mentality," then you've just told him he's not successful with women because he's not successful with women. As you may have figured out, this is completely circular reasoning. Not wrong but worthless all the same.

And yes, abundance mentality is another name for confidence, and "just be confident Timmy" is advice any of us could have gotten from our mothers (no offense mom, love ya).

STOP giving this advice. Focus on specific or technical things. Saying he needs more experience or to work on his self/lifestyle is OK too, but again, lean as practical as possible. If OP has not given anything to go on (as is often the case) then say so.

p.s. in general any advice that does not include an actual course of action is not very helpful.