Please help? Life? Psycho Issues?

i hate this week. Ok, first off, in one of my cles we are learning about the holocaust and we watched this movie called " The Boy in Striped Pajamas." Everything was fine until the last scene where they showed people getting into the gas chamber and releasing the gas. I was so afraid to a shower last night because of that scene. Then, i got over it. I let it go and I felt better today. Then, this girl in my cl researched how celebrities like Beyonce and Rhianna worship the devil. I don't know why but today i felt scared to look at my surroundings. it took me like an hour or two to forget about these two things. Now, I am learning to forget about compulsive thoughts and im trying but i need to know, WHAT IS THE PROCESS LETTING GO AND NOT LETTING SOMETHING AFFECT ME? i don't want it to be like this tomorrow when i go to a party :( i am 18 btw