Does believing in something in your personal life make that thing true?

NO. But in some situations believing some things might keep you sane and alive.

In other words you have to believe whatever you need to believe to survive your life at each and every point.

For example, even though I didn't always agree with my father or grandfather (my father and his father) I still acted like I believed what they believed in order to survive the 1950s here in the U.S. because to not do that might have interfered with my survival here in the U.S.

Also, what my father believed was not the same as my grandfather who didn't believe in religions and my father and mother were ministers in their church (at least on Sundays). So, since their beliefs were different this made this more difficult too.

However, it also made me more capable of having my own opinion even if it was different than my father or my grandfather which served me well throughout my life as a boy and as a man.