The more you do the same exercises, the better your body will be able to perform them and the less work it will take. In order to continually improve your fitness level, it is important to consider the principle of overload.
Overload is the idea of continually increasing one element of your workout, such as time, intensity, or resistance.
Here are two examples:
1. If you walk one mile at the same pace every day, your body will become used to that exercise over time. In order to progress, try increasing your speed, distance, or adding light ankle or hand weights.
2. If you start a resistance program doing bicep curls with 5 lb weights, it may initially be difficult. However, once it becomes easier, it is time to increase your weight, sets, or repetitions.