Challenges in Writing Correctly

Writing grammatically correct is not a challenge for me, as long as I have the freedom to write the sentences myself. If I am the author, then I can choose to write sentences in a way that I am confident is correct. The challenge comes when I am forced to complete grammar exercises. Because someone else wrote the sentences, and rewriting it is not an option, and I must follow strict grammar rules. I was taught most of these rules over six years ago, and have had little practice since. This forces me to relearn most of the material.