I used to have my kids hurry through the illustrating portion of the book-making. BAD IDEA!
Think of the famous authors that you've read. Their illustrations make the words come to life for the reader.
If you take your time and plan your illustrations this can help your readers too...
and
the next time you write you will be thinking of your illustrations already. Your words will become more descriptive.
So the lesson is: A carefully planned picture will improve your
current book and your future writing.
(Teachers can be so tricky. But it is true. Some of my best poets are my kids that value their illustrations.)