Custer had his day at Gettysburg where his outnumbered Michigan cavalry slammed into a Wade Hampton’s Confederate column and stopped it. Had that audacious charge not been made then the Union Infantry facing Pickett’s Charge might have been enveloped from behind.
Custer was a ‘lucky officer’. Luck is important, but it does run-out if you rely on it.
Last in their Class. Robbins, James S., Encounter Books: New York, 2006, 503 pgs.