D.T.
If you can judge a situation is going to cause him frustration, try to guide him away from it if possible. If he's playing with blocks sit close to him when things topple make a joke out of it. "Yay! Can you make it taller this time? Can Mommy help you?" If he's too worked up hold him and soothe him as if he was a baby, lots of shhhh sounds and talk softly to him. "It's ok, we can do it again. Mommy can help you."
I hope this is helpful.