Obviously Shakul not only sleep, proper breathing and positive thoughts also play role in maintaining healthy as prevention practice.
But since you have asked about sleep, I would comment on it as the way to recharge your self like batteries. It should be very optimum period of sleep. I mean to say that this should not be more or less. Sleep lesser than required number of hours (sleep deprivation) may be the cause of physiological chronic disorders like diabetes, heart disease, in the long term mental disorders like Alzheimer's disorder and obesity. Opposite to it, excess of sleep can also cause troublesome issues. So, better to keep sleep 6 to 8 hours. Quality of sleep cannot be ignored so one should take care of the good night's sleep like the following
(i) There should be gap of at least 30 minutes after dinner or last meal of the day. It is better to take last of the meal of the day by evening.
(ii) Avoid caffeine at night or late evening.
(iii) Keep always darkness in your bed room. I mean there should not be bright light in the bed room.
(iv) Electromagnetic radiation emitter like smartphones, and other similar gadgets should be in rooms other than bed room where you sleep. The radiations interfere with the sleep hormone.
(v) Sleep at the same time every night for good quality.
(vi) Begin with progressive muscular relaxation or deep relaxation technique or yoga nidra for sleep. This will boost the quality of sleep as well as induce positive thinking and autosuggestion which are the part of these techniques.