Hello Elyse, if you're confused about whether the things you're thinking are purely negative, or realistic, then it helps to weigh up the evidence you have for the belief in question.
If your tendency to be a negative thinker is deep-seated, then this process can sometimes involve several steps, because your brain will keep trying to argue with you.
For example, you mention a belief that you're not smart, no-one wants you, and your friends wouldn't miss you. You counter this by what your friends actually say to you: that you are awesome, and smart, and that they would miss you.
Your response is then: "but they're my friends, they have to say that".
What's the challenge here? Where's the evidence for this statement? Where is the rule that friends have to say nice things about you? If they believed the opposite of those things, why would they be friends with you?
Just because we believe something (I am stupid, worthless etc), it doesn't make it true. In addition, things can be true whether we believe them or not (that your friends think you're awesome).
The take-out lesson here? Beliefs are faulty and not always to be trusted, especially when evidence that contradicts them is right there in front of us. The key here is to try and let go of the beliefs that are serving you no purpose other than causing you misery.
