Stop watching video guides for normal and hard dungeons/trials. They will contain spoilers and besides, part of the fun is running content blind and learning the mechanics from experiencing it. Who cares if you make mistakes and die? You'll get better as you practice. Most people you meet in the duty finder will be friendly enough to accommodate new players on their first runs.

It's just a game, no need to take it seriously. If you ever encounter someone who gets upset for mistakes that you make, then that's their failing for taking the game seriously. Thankfully, most people aren't like that.