Hi, hope you don't mind me writing, I joined only some days ago.
Some time ago I was exactly in your same situation, and I was obliged by the situation to be something I never thought I would be, and see all my dreams shattered and apparently the life I always dreamed about ending.
What really helped was to make a list (! crazy, I know):
I made a list of all the minor interests I always neglected or made jokes about because they seemed impossible, like becoming a rockstar, or making video games, and things in my personality that I thought were lacking like being generous, and understanding others.
After some years I am not a rockstar, but I have more things to share with other people, a job I like close to video games, and next week I am going to play with a band of "oldies" like me
(understanding others, that's still an unreachable goal).
What I want to say is that "security guard" might be not very inspiring (still better than other jobs ;-), but you don't have to be "just" that. You can be the greatest person who ever was a security guard
and maybe in time you ll find something else, and a partner, and you never imagined you life would have turned out like that.
It's really mindblowing when you think about it, possibilities.. but for that, you need to see your power, and that lies in the crumbs of your life, things you are passionate about, small things that you really like to do and wouldn't do any other way, things that make you "you".
Sorry about the disgusting optimism, I hope it is a bit infectious
PS actually by being a security guard you get loads of time where you don't have much to do, isn't it? that's a plus to follow other interests