It is said that a surgeon should never performs surgery on his family members or on anyone he is emotionally attached to. The reasons being that emotions block the objectivity and thus the quality of surgery.
Pretty much same reasons prevent us from maintaining healthy lifestyle. We all know that healthy lifestyle involves eating healthy, keeping away from junk food, keeping up with good exercise program and so on. However, none of these activities are fun and therefore only few of us able to keep up with them.
In other words, our emotions and feelings of short term discomfort (whether it is due to exercise or limiting to healthy food or craving for junk food) come in the way of our logical mind, which agrees that following a healthy life style is indeed the right thing to do.
The root cause though is a misunderstanding we have about ourselves. We believe that our body (and mind, which is in a way, part of body) are parts of us. But Nirvana Shatkam will tell you that that is not true. YOU just happen to own a body, just like YOU own million other things like car, house, the shirt you are wearing and so on.
If YOU start believing in Nirvana Shatkam and start practicing this belief system, YOU will lose any emotional attachment to your body. But YOU will treat it as an extremely important commodity, which is necessary for your very existence. This will motivate you to keep it in the best possible shape and form. Off course, since YOU have no emotional attachment to this body you own, its short term discomfort will be of no concern to YOU and maintaining ideal health will become piece of cake.