"The Elements of Style", by Strunk and White, is a great little book loaded with writing helps. They state on pages 72-73:
“Do not overstate.
When you overstate, the reader will be instantly on guard, and everything that has preceded your overstatement as well as everything that follows it will be suspect in his mind because he has lost confidence in your judgment or your poise. Overstatement is one of the common faults. A single overstatement, wherever or however it occurs, diminishes the whole, and a single carefree superlative has the power to destroy, for the reader, the object of the writer’s enthusiasm.”
Need I say more? This little book is packed with insight and helpful tips for any type of writing. I highly recommend it.