Increase physical activity naturally. If you are comfortable with your current level of physical activity, let the time you give it increase naturally. Do not force it, or it will become a chore. But let yourself enjoy an extra night out dancing or bowling, a day on the golf course, or walking in the park. The keys, again, are fun and frequency.
Get plenty of sleep. People need rest. Chronically tired people have no energy to exercise. Often they feel so out of sorts that they are tempted to prop up their flagging spirits with food or alcohol. There is no substitute for adequate sleep.