I had a coworker tell me the other day that single pilot IFR is unsafe. I guess you can only go up from there...

To answer your qestion, you learn to prioritize. Yeah, there is a crapload to know to be a 121 Capt. On the day of your oral, you probably know half of it. Six months later is kinda scary. But you get out there and get the job done day in and day out, and things just kinda fall into place.

For myself, you learn to not sweat the small stuff. Prioritize.....