It is great that you have different types of friends that you can spend time with and enjoy a variety of things together. It also sounds like a few of those friends are leading you to do things that are not so good for your happiness. Remember you chose who to spend your time with and how much time you spend with them. When you start to get frustrated with friends that you have trouble with...go hang out with someone else for a while.
At school, just walk away for a while, walk to class a different way, or play something else during free times. You mention being a rookie, I am not sure what you are referring to, but remember to focus your choices on being a good person. It is better to stay a rookie at some things that aren’t good for you.
You mention not wanting to lose friends to a stupid mistake. Do you mean if you were to stop being friends with that one person? Talk to your friends about how you are feeling, they will understand. Also keep talking with your sister. You are blessed to have a sister to talk to that understands you!
Keep using your journal to work through your difficult times, you can do this!
Lisa, Crisis Counselor