A teaching from Rabbi David of Kotzk
The rabbis of old (in Midrash Rabbah) taught that when the Israelites were getting ready to sing, after having crossed through the Red Sea to safety, the angels in heaven wanted to sing first. But, God wouldn't let them—God insisted that they wait for the Israelites to finish, and then take their turn to sing.
Why, Rabbi David asks, did God insist that the Israelites go first? Because, angels are perfect, holy beings, and so they are always ready for holy moments. But, not so with people. We're forgetful, and easily distracted*. Even though we were ready to praise God with a full heart at that moment, we couldn't be sure that we'd still be ready in a little while. And so, we had to take the opportunity, while was there, to sing, and to praise.
Remember: don't let a holy moment pass you by. They don't come very often, and when they do, they often pass quicker than we can imagine. Take a moment, appreciate it, and praise it in your own way. It may be your only chance to do so.