You've seen it happen a dozen times, most recently in this week's Smile Precure. A Magical Girl is in a tight spot. She makes a big speech about how far she's willing to go to protect her loved ones, and then. Shiiiiiiiiining light comes from within her, usually from the transformation object, which is usually a broach on her chest.
Nine out of ten times this leads to either a new transformation or a new attack. Either way it typically turns the tide in favor of the Magical Girl. This power is one of the reasons the final battles are typically the best. All of their love and determination goes into it, the characters are at their peak maturity and the results tend to be amazing. The finale of Heartcatch sure was.
I've gotta say this is one of the things I really like about the genre. It's not about simply gaining a random powerup ala Bleach. It's about the growth of the character and their drive to protect their loved ones. So often friendship speeches are looked down on by people who don't like the genre, and I admit sometimes they're unnecessary (like every filler episode of Heartcatch) but when things get really tough, those speeches are a testament to the love and friendship these girls share, and how far they're willing to go.
A Magical Girl's power should be as limitless as her love and desire to protect those she cares about, and moments like these just exemplify it.
Subject: The Power of Love/Friendship 
