A daily running habit has become so ingrained it feels obligatory, not optional. After a late night and low motivation, the speaker runs anyway because it's part of who they are. The shift from wanting to do something to needing to do it is what makes a cornerstone habit stick.
You know when you just don't want to get up and you don't want to go and do anything? I had a really late night last night and honestly the last thing I thought about doing was coming out for a little run this morning, but, but I knew that it would make me feel good and that's what happens when you kind of get this thing that when you have a keystone habit or a cornerstone habit whereby you do exercise of some description every morning and it just then becomes part of your identity, that actually if you've got— that you've got to go and do it. You've got to do it regardless. And here I am doing it regardless.
