In order for us to develop, grow and expand, it is necessary for us to take on new challenges. Life is about continually learning and expanding. We feel at our best when moving toward something wanted, and we move forward by accepting challenges. For example, you may challenge yourself to read a particular book, learn something new, commit to a process or technique, give up a bad habit or anything else that you want to do.
The challenges that you take on should not be too big because then you are setting yourself up for potential failure. Attempting to jump a gap that greatly exceeds the range at which you can jump will only serve to be counterproductive. On the other hand, challenges should not be too small because you would then fail to stretch yourself enough to grow, expand and develop. Therefore, by taking on challenges that are too small, you will not better yourself or accomplish new and bigger things.
So, when challenging yourself, you should ensure that the challenges are neither too big nor too small. Essentially, challenges should not be so big that they are greater than your present capabilities, and challenges should not be so small that they are too easily accomplished. You must take on challenges that are within your capability range but at the same time will stretch you beyond where you are now.
You can measure the challenges that you take on by deciding if your challenge is a preference or a demand. Gradually getting fitter would be an example of a small but rewarding challenge. Similarly, doing a charity bike ride for the first time would be both challenging and rewarding. On the other hand, becoming a famous actor overnight, or training for a marathon in a week would be an example of a demand because it would create too much pressure. It is about creating challenges that are preferences rather than demands.