There were so many people at the beach party that no one noticed me packing up some of the belongings and leave.
Why would you steal other people's things?
I don't normally do this. It was just too tempting.
That is wrong for you to do with people that trust you. You shouldn't take things that belong to others even if they aren't watching. It will be hard for people to trust others again and they will not trust you either.
What is so hard about taking things? It's not like people are going to care.
People do care if their things are taken. Wouldn't you care if someone stole your most valuable item?