Getting Up After "Falling"

Yesterday was not a good day at work. Was doing some follow-up on some training program and ended up being insulted by the employee. Morale was really low. It bugged me.. for reasons like it's awkward to face the colleague and hate this type of "spoiled" relations between colleagues. It also had me pondering how long I will let this continue to bug me. Am I just so small in character, that I cannot stand up for myself and move on?