Even just being ready to help when called upon is a mental and psychological exertion, though, because you are at the ready, just in case, and expected to be able to save the day no matter what happens.
Don't downplay yourself!
In the group of three, where was the one you did? Did you do your own first and then help the others, or where you later in the day? That is what would have made the difference for me. If I did my own first it probably would have been cool. If I helped out with two others and then went to do my own I would have probably been a little spent...