If today didn't go how you thought it would...
Or if you felt that you "failed" at something (even if you really didn't, because your expectations were probably too high).
There's always a new day, new hour, new minute to try again.
You don't have to wait until Monday. You don't have to wait until the weekend. You don't have to wait until the start of a new month or new year.
You can start right now.
Every minute, every second is a new beginning.