Stories with lots of active verbs glow while those with mostly passive verbs appear gray and dismal. I think what often happens is that we write a first draft and the passive verbs come to us automatically as we strive to get the main idea of the story or nonfiction article across. That's fine, but we can't let it stay that way if we want to see it published someday.
Let the piece simmer a day or two or even three, then go back and make revisions. To begin with, go through the draft from start to finish and mark every passive verb you find. If you're computer savy, you can set a program to find how many times you used was, is, are, went kind of verbs. But you can do it on your own in a short time, too.
Then look for active verbs you can substitute for the passive ones. Be careful not to repeat them. Those repetitions stand out more than you think. Read the story with the new verbs, and I feel quite certain you'll find a far more interesting piece of writing than that first draft. Then it's on to other revisions.
An exercise to help: Take a sentence with was in it and rewrite it in as many ways as you can using active verbs. Sometimes, you may need to reverse the order, not just insert a new word.
Mary went to the store.
Mary ran to the store.
Mary drove to the store.
Mary strolled to the store.
Mary flew to the store.
In the first sentence, we have no idea of Mary's mood as she makes a trip to the store, but in three out of the next four, we have an inkling of what her mood is.
Now try a sentence like this one: John and his horse went over the fence. Find active verbs to show the reader how they went over the fence.