Your first time? You
grow on witcha bad self! Very well done!
Now I'll have to warn you that hand-in-hair is a disease that will become second nature, particularly because you didn't braid to the end; but also because new human hair can be a pain as it unravels easily. You might find some on your pillow or God forbid one falls off your head onto a classmates notebook as happened to me in college! But in time, the hair gets "trained" and hold on much better.
So you'll get into the habit of feeling through your hair to find any that needs redoing, either from getting loose on its own or due to new growth. Now the growth part is fun if you do what I do and just redo them w/o bothering to check length. (I usually feel for loose braids while watching TV and redo one at a time w/o checking length. No comb needed either. Just undo with fingers, separated strands with fingers and then put extension back. In a few months, you just happen to look and it's excitement galore as you wonder where the length came from. That's the joy of doing your own hair. You can redo the braids as they need it and thus prevent the matting that causes breakage and also the painful swinging that causes the braids to fall off with your hair. And you do all that lovingly and with the care that only you can give your hair.
Just make sure you keep your hairline tidy--redoing any that get loose pronto--and you'll have a wonderful journey in braids. Don't be surprised if you get addicted like somebody we know.