Start doing and develop a habit: it usually takes three weeks, 21 days.
But,
What habit is actually formed?
If you exercise for 21 days, each time making a martyr’s face and waiting for these 21 days to end, then these 21 days in reality you develop a habit of negative feelings about exercise↑. And when the 21st day is over, you most likely will not do exercises.
And if you got together for 21 days and did exercises cheerfully and with pleasure, this habit will really be a habit to do exercises in the morning.
A more general rule: whether a habit becomes a character trait depends on the addition of several circumstances: if a person understands the meaning, the need for this new habit; if a person’s new actions fit well into his lifestyle and are supported by his environment; and finally, if visible positive results from the acquired habit begin to appear soon↑.