Well, that's just it. Discipline is not motivation. What you had was motivation. What you need is discipline.

Motivation is wanting to go, and that fades. Even if it's something as simple as "it's freezing rain right now" will make it at best less-fun, and lower your motivation.

People commit to new things when they are disciplined. That doesn't mean you find a way to always feel like going, cuz that's unlikely to ever happen. You remove the "feel like" from the equation, and you just always go.

It's not as "fun" an attitude but it's the attitude held by most of the people who commit to positive lifestyle changes.