Updated: Mar 1, 2020
This is often the most common reason students leave any physical discipline. We know that physical activities (martial arts is no exception) run the risk of injury, both short and long term. Illness is another factor with the same effect.
One of the truest forces in the human experience is Habit (if you have not read The Power of Habit, check it out: https://www.amazon.com/Power-Habit-What-Life-Business/dp/081298160X/ref=sr_1_3?ie=UTF8&qid=1534886578&sr=8-3&keywords=habit)
Like diet and exercise, the pursuit of self improvement is an upward battle, our minds are constantly battling against us because of our ancient drives for self-preservation and energy conservation. Injuries and illness are a great excuse for our "ancient drives" to interrupt these habits - opening up the opportunity for bad habits to replace them.
If you read Mr. Duhigg's book, you will find that there are generally three components to any habit and when you replace the positive action of training with a negative one (like sitting on the couch eating junk food and binge watching tv) while achieving a positive feeling - your mind will quickly opt for the sugar and tv before the rigors of training.
So what's the secret?