Very insightful and I agree. Another common mistake is lack of diversification in markets. Most will stick to a particular market (win/loss/draw for example) without the knowledge of the additional underlying markets that exist for a given bet. Talking strictly soccer, I tend to favour team markets (win/loss/draw, both teams to score, under/over 2.5 goals, under/over 3.5 goals etc.) and I'm always looking for the right market for that given fixture at that time.
RE: The BIGGEST mistakes people make when sports betting (and gambling), and how it prevents them from being profitable