Investing at 18, What do you wish you knew earlier? Canadians

I just turned 18 and started saving with two goals in mind which are retirement and eventually buying a house. I also want to put a small amount into higher risk assets just to learn how things work. What do you wish you knew when you first started? What are the biggest mistakes beginners should avoid? Also how did you land on your first investment strategy? I am just trying to build good habits early and learn from your experience.