It took me years to figure out, and I'm still learning, what not to say and do around my wife. Men, we have a long way to go in understanding the woman.
The right lingerie can make a woman feel confident and sexy. If chosen badly, it can make a woman feel awful, not only about herself but you too. As much as you'll enjoy seeing her wear it, first and foremost it's important to remember that this gift is for her - not you.