Balancing your drive to attain a goal and the perspective you use in attaining that goal is critically important. As soon as you push too hard, or elevate your desire to reach a goal into a need or "have to" you can begin to create disruption and unnecessary pressure. This unnecessary pressure then gains its energy by depleting the energy you otherwise would use to move toward your goal.
This is why its important to understand the energy of "doing what you want". When you truly want to do something and/or can see the value to you or others in doing that something then it gives you energy. On the other hand, when your motivation to do a task changes to a perspective of force and control, as soon as it turns from a desire, a joy, an inspiration to an imperative, the energetics change and you run out of energy for the task at hand.
What you can look for when you do a bit of self reflection is quality motivation. Motivation that comes naturally from within you which is associated with enjoyment, fulfilment and motivation, that might be external (like advice from another person) but that you can buy into because you can see the value of the task at hand.
When you find quality motivation you can energise yourself to keep going when things get uncomfortable or challenging because this type of motivation is psychologically sustaining. It gives you energy, rather than taking it away.