[Mz]

How to solve this problem? Honest question.

Honest answer: Consider the possibility that you may have a hidden health issue. Look into that angle. Addressing my own health issues has been the single biggest boost to my productivity, ability to concentrate and ability to stop being a serious hardcore procrastinator. If you simply lack physical energy and ability to concentrate, willpower is not going to overcome it.

Best of luck, whatever the answer turns out to be for you.