It makes your life infinitely simpler if you don't renegotiate with yourself when it's time to do something.
"Ohhhh, I don't want to go to running, it's raiiiinning out..." --
how many thought cycles does that burn?
Does anything useful ever come out of that conversation with yourself, when you're debating if you'll do the right thing or not?
A short phrase that's useful:
"A smarter me chose to do so."
"Because a smarter me chose to do so."
Oh, but I don't want to do.
"But I'm not as smart right now, and a smarter me chose to do so."
Helps immensely when tired, fatigued, and not thinking clearly. Rethink your plans, occasionally. If you really genuinely think it's become pointless to go running, make a note to review that tomorrow morning or during your next weekly review, and decide to amend or cut your program.
You still need some judgment. Don't run if you're injured. But the vast vast vast majority of the time, it's not injury or anything legitimate. It's just that natural human pushback against self-development, laziness and indolence setting in.
"A smarter me chose to do so." That's why you do it.