Certain advice on how to become a better writer is nonsense in my opinion. I will go to the opposite extreme and tell you to lower the bar on your personal expectations, and wisely not let anyone else dictate what is best for you.
You don't have to tie yourself to the computer or your journal every single day for a set number of minutes. That's torture in my estimation. Remember that professional writers are editing, marketing and promoting their materials, which is a form of on-going writing in itself.
Writing doesn't happen just because you decide to dedicate early mornings to the craft. It could come at any hour of the day or night, or maybe not at all, for several empty days- hopefully not weeks- in a row. When your mind is ready to release the words, they will appear effortlessly and in beautiful sentences. Otherwise, be out in the world enjoying what life has to offer you.
Writing doesn't need to planned carefully either. If you permit the muse within to take control, you will find how exciting the creative process takes care of you all on its own.
Practice. Play with words. Enjoy.