Your root cause suggests you may have been feeling a little off balance, perhaps for as long as three or four years. You feel you missed opportunities - real or imagined - and doubt may have been gnawing away at you. 

This combination can leave you feeling a little insecure about where you belong and what you should be doing, not unlike a rock climber suddenly experiencing fear of height halfway up the mountain. Nothing has changed; you are climbing with the same equipment, traversing a mountain like many you have climbed before, but your discomfort is real, nonetheless.

Insecurity and doubt have a positive side as well. They help you move forward more carefully and deliberately, thereby proving to be the very ingredients that can prevent you from taking a hard fall.