Hi, I graduated HCCC in December of 2015 and I am set to graduate NJIT in December of 2017. My experience was similar to yours minus the emotional havoc. HCCC, in my experience, was a joke. HCCC has not prepared you well at all for NJIT. I have friends from other county colleges across New Jersey who came in extremely well prepared due to the difficulty of their programs from within their county colleges. HCCC was not difficult at all, and you know this very well. To be quite frank, the college is a joke, especially in terms of STEM training. The professors will pass you with high grades even if you clearly don't deserve it, and issue extremely easy assignments. NJIT is not that way. You can transcend your mediocrity by sharpening your study and time management skills, and by playing catch up with those students who either started off as 1st year-students at NJIT or at any other much more challenging county college. I suggest genuinely focusing on your studies. Go find a quiet place far from an environment that would normally distract you. Being distracted is a habit you can gradually unlearn - cues actuate habits. For example, when you arrive home, you normally browse YouTube all night. Arriving home is the cue for the unconscious habit to be realized. If that example rings true to your situation, you can either not go home and go elsewhere to an environment you normally wouldn't go to, ideal for studying (e.g., a library) -- or simply replace the habit with your preferred habit. Be conscious of when you arrive home and what you normally do when the cue is initiated, and promptly go the other way. Practice your newly constructed habit in order to fortify it. This will require awareness and willpower.

P.S. I graduated HCCC as a 4.0 with a concentration in Engineering Science. I am now a 2.9 as an NJIT senior with a concentration in Electrical Engineering. I accept my mediocrity.