The letters S - T - U are for STUBBORN.
Yes, I almost quit this silly A-Z blogfest challenge. Holy Hannah. But, I woke up in the middle of the night with the perfect word to stay in and catch up. Stubborn. I will not quit this close to the end!! I will be stubborn and stick this sucker out. So, yes, I may have fallen, and you may consider this cheating, but I'm getting back up and finishing this marathon.
So ... there.