I’d say a ‘reality check’ is not always negative.

Say you’re very, very self conscious in public, always nervous about how others percieve you.

But then, one day, a friend pulls you aside and ‘reality checks’ you with:

“Look, in 90% of situations you’ll ever be in, if you can follow a few basic dress and behavioral rules, you’ll be fine. Barring situations where the whole idea is you making a good first impression… most people, most of the time, in most situations… really don’t care that much.”

Things like that are arguably ‘positive’ reality checks.

The reason why ‘reality check’ is often connotated negatively is because most of the time, cognitive dissonance develops as a way of excusing or justifying harmful or irresponsible behavior or inaction.

But it can be the case that reality is in someway better than it is perceived by someone who is overly critical or peasimistic in some way.

In some sense, the initial realization that you’ve been incorrect about something is negative in that you may be embarassed about being wrong in the past, but if it actually means a more realistic outlook going forward, then I’d say thats overall a ‘positive’ reality check.