I learnt to write in my professional career 30 years ago. Running a research department full of technically brilliant but linguistically challenged guys somebody had to take responsibility for presenting their findings to best advantage. And then there were the applications for new projects. It quickly became obvious that if I couldn't write convincingly and well then we would run out of credibility pretty damn quickly.
Senior managers are not assiduous readers I discovered. Long preambles and strong narrative were pointless. Get to the point quickly and make it stick hard. The more I wrote the punchier my stuff became so I started writing imaginary proposals and speculative finding just for practice. The prose got tenser, leaner, sharper. And the writing became easier. That's when I realised that writing is like any sport - the more you practice the better you get at it. My writing muscle got harder and stronger and my stamina improved. The more I did it the better I did it.
After a while it stopped getting easier but the writing became better. I got to the key points quickly, pushed them home and moved on from point to point until I rammed the conclusion, unavoidable and all but incontravertible by now, into the basket. Slam dunk.
My reports got shorter and slowly I worked on different ways of designing different presentation styles. I figured that people would get sick of the same approach every time and if I could know who would be reading it then I could tailor the attack to their sensitivities. The writing muscle was now becoming more versatile - it could manage slow starts and sprint finishes - it could sustain serve and volley or drop back and play a baseline game.
Treat your writing as a muscle. Keep it fit, make it strong, and make it versatile. It won't let you down if you do.