That sounds like something I go through too. The second I take an extra day because I don't feel like going, it's almost like having to reboot and start the motivation process all over again.
My wife and I started walking outside regularly about 15 years ago and it's been an easy thing to keep as a regular part of our exercise. Typically we go 5-7 miles 3-5 days a week from April through October here in MN. Both of us use the treadmill or Peloton during the winter months. When we are in Florida like we will be from Nov. 18th-29th, those long walks happen pretty much everday. It's now just habit when on vacation for us to wake up, have a coffee, and go on our walk. Those morning when I'm headed to the course she walks with a friend, one of our daughters, or alone.