Variety!
When figuring out an exercise plan that works for you make sure you have enough variety in your exercise routine that you won’t get bored. Variety is also important because our bodies are very good at adaptation. If we do the same thing over and over again our body gets used to it and we aren’t getting the same benefit we did when we first started. Adding variety helps to continuously push our bodies to its limits and in doing so makes us stronger. Variety can come in many forms: doing more repetitions, adding more weight, increasing the length of time, changing the type of exercise completely.
Reference:
Exercise Tips from the American Heart Association