Chances are if you are feeling that way, then you probably could have gone faster.
Try in your next race to be feeling a little tired by 1mile mark, fatigued by 2mile mark, then hang on for that last mile and give it everything. TRY to blow up. No races (should) matter until Districts/ Regionals so see what you can actually do.
I went from 18.20 freshmen year to 16.31 the next because I tried to stay with our number 3 guy one race and it worked. Changed my running career.
On the other hand, we as runners tend to forget exactly how much pain we were in at the time after the race so during your next race, think "wow I really am giving it all I have." Most runners, no matter the outcome, would like to think they could have gone faster (Lagat, Centro, El Guerrouj) even though they may take the win or WR.
TLDR: try to blow up your next race and remind yourself just how much pain you were in mid race after you ran.