Could you elaborate on that more? How long does that "excitement" last for? A few hours, a few days, weeks, etc.?

If it lasts for a few hours, it could be your personality or it could be something like borderline personality disorder (BPD). You did say "There are times during the day I feel very happy, frustrated, and at night or when I am alone, I tend to feel anxious, paranoid, or sad." which suggests your mood might be highly changeable?

Borderline Personality Test - Psych Central

It might also just be anxiety/depression like Keegan2015 and RomanJames2014 suggested.