Why is the Earth spinning (at approx 1,000mph at the equator)? Why aren't we slowing down?

Gravity holds our sun together, sustaining its nuclear reactions, which supply our needed heat and light. Gravity keeps our spinning earth in orbit around the sun—making day and night and seasons—and prevents us from being thrown off like mud from a spinning wheel. Earth’s atmosphere is held in place by gravity, while the pull of gravity from the moon and the sun generates regular tides that help circulate the waters of our oceans.