There are two types of of human motivation, intrinsic and extrinsic.
"Intrinsic motivation is defined as performing an action or behavior because you enjoy the activity itself. Whereas acting on extrinsic motivation is done for the sake of some external outcome, the inspiration for acting on intrinsic motivation can be found in the action itself." (www.study.com)
When it come to exercise we might use the following examples to explain what motivates. Someone who is intrinsically motivated to exercise would do so in order to be healthy and to feel good. He knows that he will reap many physical and emotional benefits as an outcome of regular exercise. This type of person might appear compelled and driven as they plan and execute their exercise routine. Most likely this person will make exercise a priority in their life.
To be extrinsically motivated to exercise involves an outcome or reward such as winning a contest or earning a medal at the end of a race. This person may need a a continuous supply of unique motivators available to them in order to be inspired to follow an exercise routine. Always on the lookout for something new and exciting to spur them to the gym.
I definitely lean towards intrinsic motivation but have a strong dose of extrinsic motivation as well. Actually, my extrinsic motivation is something relatively new to me. Four and a half years ago I started running in a serious way. My goal was to complete a half-marathon race. I liked the idea of being a part of an organized, sanctioned event where as a participant I would receive a nice shirt and as a finisher I would receive a medal. For my first race I had a very modest finish time goal, but that may dip into the intrinsic realm.
I try to encourage people, (clients, friends and strangers), to add some extrinsic motivator to their exercise toolbox. There is a strong psychological element that can assist people with their exercise planning and with each session. I know I often struggle to complete a difficult session but extrinsic motivation helps me overcome the challenge.
Find your inner strength, but also find something to reward yourself at the end.