The extra bit of line may hold the knot if it slips. Use finger nail clippers to trim your knots. Your dentist bill will thank you. Cut of minor nicks and cuts on your leaders and mainline Make sure you have enough wraps on your knot. I had a fish during our local derby pull my knot out.
Experience is a rough way to learn.
On hooks never tie a knot to the hook eye unless the hook is designed for it. Tying the knot on the eye puts extra stress on your hook shank and eye. Big fish will shear off or straighten your hook.