If you're looking for an idiomatic expression, something along the lines of swallowing the bitter pill might fit the bill.
The thing with this expression is that it can also be said of accepting a reality that one does not want to accept, so it also carries the connotation of knowing that something is real and good, but not wanting to carry on with it.
An example in usage:
A: You know, you really should see a doctor more often, even if you're not sick. It helps you keep your health in order. It's also better to know everything is alright, than just guess at it.
B: You're right. I hate going to the doctor, but I guess I'll swallow this bitter pill, suck it up, and go. I haven't been in a while, after all.