It is very powerful indeed. Another aspect of it is how we relate to other people.
For example, in recent years, I made a more conscious effort to smile and say hello to people, even when I was feeling down, and then made a point of trying to remember their first names, plus a bit of info about them, so that I could ask a bit of a personal question about them, such as, "Did you get your car fixed? / How is your son? / Are your kids settled into the new school etc etc, in fact anything to make them feel that they were important to me.
Two things happened, first of all, I felt a true warmth and friendship develop, and secondly, what started out as me consciously acting something out to disguise my own lack of confidence, in fact boosted my confidence, and led me to begin feeling more empathy towards other people.
I think that this was the power of suggestion, and SELF suggestion, and although not a 'cure all', it certainly helped me.
My family sometimes laugh and say, "You seem to know everybody. It seems that way to me too.