Feeling down can sap your drive. Exercise can help to build up your drive. Here are some tips on exercising.
Try lots of different activities until one of them clicks. A friend of ours was so bad at football and other school sports that he was excused games and allowed to do music practice instead. He left school with the label 'No Good At Sport' firmly attached.
Over the following years, he tried his hand at many different activities and was equally useless at all of them, confirming his self-belief that he just wasn't the sporting type.
But then he tried windsurfing and discovered that he had a natural affinity for it. He quickly became expert and was able to discard his non-sporting label once and for all. With this change in attitude and a renewed sense of self-belief, he then became adept at several other sports, and in his mid-50s actually qualified as a ski instructor. His PE teacher would not have believed it.
Try building exercise into your everyday domestic activities. An American friend has this down to a fine art. Waiting for the kettle to boil provides him with the opportunity for 30 sit-ups. Heating up a ready-meal in the oven creates just enough time to perform a 30 minute fitness routine. By the end of the day, he's packed in an hour's worth of exercise without even noticing it.