For me, it's starting a business. Specifically, being my own business. There's no HR department. No billing department. No social media manager. Just. Me. I haven't been this nervous about something since I packed a (tiny) U-Haul with all of my things and moved down south to get married!
This is scary, ya'll!
Doing something new and challenging does not mean never being scared. To quote one of the most amazing human beings to ever grace this planet, Nelson Mandella:
"I learned that courage was not the absence of fear, but the triumph over it. The brave man is not he who does not feel afraid, but he who conquers that fear."
So don't be afraid of getting up, getting moving, trying something new, and pushing yourself harder today than you did yesterday. You only have today, and you can't waste it caring about scary!