You are a complex human beings who experience life on several levels- physical, mental, emotional and spiritual. These are the four planes/levels that real fitness/health take place. All change work occurs on all levels. And the results and benefits occur on all four levels
Emotionally,you can experience a new heightened self image, achieving fitness goals leads to self confidence, improved body image and discipline.
Mentally, being fit and healthy effect over all immune system, meaning a better work and school performance, and fewer missed days at work and school. Also the there is an increase in oxygen which flows throughout the body especially the brain.
Spiritually, you can ask a professional athlete if training is a spiritual experience and they will always answer "yes." Now many people roll their eyes when you start talking about a professional athletics. As if they cannot relate to them. But we can learn a lot from a professional. About their thoughts, their attitude etc. And the respect they have for their temples. Ask any great spiritual teacher and they will tell you the importance of bringing the spiritual connection to the physical.
And of course physically,there are so many changes that occur. Here are just a few;reduces the risk of injury, strengths the heart, lowers blood pressure, assists in anti-aging, digestion, skin, hair etc. Everything depends on circulation and the only way to get things circulating is by moving.
Make your changes count on all levels.