Through routine exercise, your body gradually builds strength and endurance. However, if you keep your workouts TOO routine, those benefits begin to stagnate. Therefore, it is essential to periodically change your workouts so that your body will continue to reap the most benefits from your efforts.
Why is change crucial?
If you follow the same exact exercise routine day in and day out, your body becomes accustomed to this routine. As the body adjusts to the same workout everyday, it is normal for the body to adapt on a cardiovascular, respiratory, and cellular level. Over a period of time, following this same old routine causes the rest of the body to adapt, as well. As a result, any further physical improvements become limited, and your training becomes boring.
But, wait! There's still hope! By incorporating even slight changes into your exercise regimen, you are able to kick-start the body once again to move towards those gains you've been striving for!
What kind of changes should you make?
Even the smallest change in your routine can make a difference. Below are a few suggestions:

Change the time of day at which you exercise.

If you prefer one type of exercise, such as running, change the exercise, itself, in some way. For instance, increase the intensity level or the length of the workout.

Try a new type of exercise. Introducing a new exercise into your training will ultimately work the body in a new way. Different muscle groups may be called upon to perform, thus, challenging your body to some degree.

Alternate among a variety of exercise routines. You may mix up your routine each day, or you may alternate between one routine one day and another routine the next day. This keeps your body on its toes, so to speak...and, it helps prevent exercise boredom.

Periodically change the location of your workouts. Even a simple change of scenery can keep exercise more exciting. Such a change also has the potential to boost your energy level and improve your training.

Life can be tedious. We often find ourselves in a rut, doing the same things day after day after day. For a more exciting life and better fitness, change your workout routines from time-to-time. Your body and mind will thank you!