He rares himself up?

Solution 1:

You might consider psychs himself up

The Free Dictionary defines it as:

Inf. to get someone excited or mentally prepared for something. I psyched myself up to sing in front of all those people. The coach psyched up the team for the game.

and

psych somebody up - to make someone enthusiastic about something they will do [...] Tim was psyching himself up to run the 26.2-mile course.

Solution 2:

Well,

rare chiefly dialectal variant of rear

rear verb transitive verb

2

c \ˈrir\ (audio pronunciation) dialectal, chiefly England : to stir up to action : arouse

Merriam-Webster Unabridged Dictionary

thus in principle one could say

"rare myself up" to mean "arouse myself [to enthusiasm, etc]"

Problem is: it's not there, it's not idiomatic, as others (Peter Shor and Hot Licks) have observed already.

It's used only as "to rise to his full height," like a lion/horse does, on its hind legs.

An Ocean Free Lance: A Novel - Page 280 William Clark Russell - 1896

... and rearing himself to his full height, he thundered out in a voice positively hoarse with passion; “How dare you order a delicate boy like him into that dark rigging?”

I'd suggest instead:

"/hustle/hurry/rush/push/drive/compel/bestir/rouse/arouse/commove/agitate,/excite/ himself to excitement/enthusiasm"

or the common

"pump himself up"

Solution 3:

You can use it similar to this, though usually one would say "He got himself all rared up." This is still common usage in the American South/Southwest, though it would be considered more odd in other parts of the country, so consider using it if the character you're writing for is either older or Southern, and consider other terms if they aren't. "Psyched himself up" would be something a young person would say.