Thanks, David and Jeff!
Jeff, this is not "over" posting, I think that we can have good discussions here. I think that perfection must be the goal, the ideal to be pursued, but it must not paralize us. I do my best today, but I know that tomorrow I can do better. We learn everyday, all the time. We must go on and on, and learn with the mistakes.
When I started to use Storyline, I followed the tutorials showed in the begining (Getting Started, Inserting content etc). I watched the videos posted by Jeanette, and I wanted to narrate like her. It was very difficult to me, I never had made voiceover before. Each slide was a drama, but I achieved results that I considered good. It wasn't excelent, but was satisfactory.
Later, I learned a lot of things in this community: how to use the sound editor to cut pauses and hesitations (but not ALL the pauses), use Audacity and Levelator, microphones... the results improved, although they're not excellent yet.
Maybe some day I should try to prepare a screencast using Screenr or Replay...