Jealousy and narcissism. I didn't know they were there when I asked him to help me.

[Kirk will never know for certain if Will intended to kill him with his nanites or if the vampiric transformation was an accident that Will doesn't regret. Either way, Will had betrayed him.

In retrospect, Kirk knows that his struggle to cure himself of vampirism was largely because Will was secretly sabotaging him the entire time. Kirk had put so much trust into him. It'll likely be a long time before Kirk stops feeling hurt by Will's betrayal, if ever. He loved Will and Tina]

I thought we were friends. It used to always be just three of us.

[An understatement for a deep wound. It was also then that Kirk realizes he's divulged more than enough already]

The point is this endeavor could be very difficult. I had my own struggles when I tried to treat myself.