mental block
A mental or psychological inability to do, think about, confront, or undertake something. I have a bit of a mental block when it comes to swearing when I'm around my parents—they were very strict about it when we were kids. It's like she's got some mental block about accepting adult responsibilities.
* mental block (against something)
Fig. to have some psychological barrier that prevents one from doing something. (*Typically: get ~; have ~; give someone ~.) Perry has a mental block against speaking in public.