The power to change one s own physique is one of the biggest appeals of weight training, if not the biggest. Lifting weights is a solo activity over which you alone have the power of control. Once you know what to do, you need rely on no one. No matter where you are now big or small, strong or weak, young or not so young you need only compete with yourself. It is you, against you.
Progress is measurable, and concrete.
It can be as little as just one more rep than last week in a given exercise, with the same poundage. Or it could be the same rep count but with an extra pound on the bar. Or it could be one of several other indicators of progress. All of these small doses of progress are little thrills you will never tire of. They make weight training a fabulous activity.