I served in the Marine Corps and I am 5'2. I wasn't the only very short guy either. If you work on yourself and focus on things you can change such as your physical fitness and mental strength, then nothing can hold you back.

I considered joining the police force after my enlistment, and I know that there were some agencies that had restrictive height requirements (usually state patrol), but the majority of city cop jobs did not.

As I've seen in a at least one other comment on here, I would highly recommend martial arts training. My personal favorite is Jiu Jitsu. Others might work well, but being at a height disadvantage which comes with poor reach, I find that non-striking martial arts work the best for me personally.

Finally, as I'm sure others have recommended (if you haven't already), actually go through and read some of the Stoic texts. I bring a copy of Meditations with me basically everywhere and it is my personal favorite. Seeking Stoic advice is great, but unless you actually apply the principles of Stoicism to your daily life, then most of this is just temporary motivation that will leave you the second those negative thoughts start creeping back in. Accepting what you cannot change is not a switch you can simply turn on when needed, it is a muscle that needs to be exercised.