In music writing (both a hobby and passion) - most of the rookies I come across (especially in rock and blues) think theory is too hard and too limiting, and that playing by ear alone is the nirvana of spirit-to-music.
In poker (both a hobby and a passion) - most rookies will over bet any hand containing an Ace pre-flop from any position (particularly weak Aces) then over play them if an Ace hits any board texture. For instance, holding A4 is typically a mediocre to bad holding against a tight player on a board like A T K. The tight players are frequently going to have at least 2 pair, a set or straights in these situations, or if not, an Ace with a higher kicker which is going to play much of the time.