Learn to be a kiss a$$. Keep your mouth shut unless spoken to. Never disagree with your "superiors" even if you know they're wrong and you're right. Remember there's more to it than being good at the job - you have to be "one of the lads" socially too. (My experience is that's more important - I had some real w@nkers promoted over me and then fail Controllers courses). Never express an opinion - "yes sir, no sir, 3 bags full sir" is the order of the day.
Do the above and you'll find the becoming a Controller in the military has more to do with having a face that fits and less to do with having any controlling ability. (Though very embarrassing when you fail to validate as happened to one of my contemporaries.)
I had the same hopes as you at your age - if I had my time again I'd be banging on NATS door now rather than becoming a civil ATCO later.