Use external reminders to help you stay on track when you're not at your best.
When I'm at my best, I often overestimate the judgment I'll have when I'm depleted.
When I've exercised every day for 100 days, on the 101st day my brain reminds me when I haven't.
When I'm tired and achy and stressed, an exercise routine a distant memory, that reminder is gone.
It can survive a gap of a day. But what about a week? A month? A year?
What if your circumstances change and the old routine no longer works?
External reminders seem superfluous when I'm doing well. But I cherish them when I've lost my way.