For example: I was afraid of the water. Then, I tookswimming lessons. Now, I am a lifeguard at the neighborhood swimming pool.

You do not have to force your statement into using the verb "was."

Here is another example: I used to believe everyone had good intentions. Then, I met someone who manipulated me.Now, I am more careful about whom I trust.

You can try this out with several topics to find one that appeals to you. Once you have chosen a topic, think about an event you can retell to explain the lesson or change.