No I don't feel bad about killing an animal! As others have well said, hunting is really about population control. Limits are set to keep deer at healthy numbers, so we are doing the herd a favor. I feel very bad about a poor shot, when an animal suffers needlessly! When you think of all the ways to die in this world, a bullet to the heart, is not really a bad way to go!
And if theres still any doubt, remember the Lord gave the world, and the animal kingdom to man to subdue!