Being comfortable with being uncomfortable is a decision. You don’t become comfortable because the situation has changed. You become comfortable because you decided to be more reasonable than emotional—to control your mind in a tough time. Waiting for a circumstance to change is futile. By the time you think conditions have turned in your favor, something else pops up to negate that change.
There will always be something that makes you uncomfortable if you are moving and progressing, and that’s as it should be. It seems like a catch-22: You’ll become more comfortable in X situation by spending time in X situation, but you are too uncomfortable to spend any time in X situation, so you never become acclimated to it.
So, your first action is to force yourself to do that which is uncomfortable. From great boxers* you’ve learned that adapting is the key to winning championship bouts. Prizefighters become prizefighters when they are faced with an unknown situation and find a way to overcome it. Emulate them and remain reasoned in new fights.
*Specifically Andre Ward. In an excellent two fights against Sergey Kovalev, Andre Ward demonstrated an amazing ability to adjust in the middle of the fight and take control of his own fate, as Max Kellerman might say.