If you want something to stick, do it everyday.
That's what we did with exercise. We do it everyday, not three or five times a week. It doesn't have to be an intense training all the time, as long as we do some form of exercise 45 minutes everyday. It varies between running, yoga, functional strength training, and walking (usually reserved for when we don't have much energy).
Why everyday? Because it lessens the friction. We no longer have to ask ourselves: Do we exercise today or reschedule to tomorrow? Having to make that decision everyday, to choose today instead of rescheduling it, takes a huge amount of willpower.
Instead, the questions becomes: What exercise do we do today? Showing up is no longer optional. It's been decided. That step has already been taken. And the temptation of rescheduling is eliminated.
And, it becomes habit. If you stick to a morning routine long enough, the steps become automatic. You get up, brush your teeth, drink a glass of water, change into your workout clothes, and start warming up. It's simply how you go about your mornings. It's where your body takes you, without conscious thought.