Here's my take:

Sometimes I'm great at it, and sometimes I'm not. For me it has everything to with being in the zone. As an owner/installer (one man show again) I have found when I spend the day looking at stuff and bidding, I start to do really well. I'm comfortable, I'm confident, but not cocky,
I'm personable and friendly. Then I sell more work than I can handle and get frazzeled. My people skills suffer because I'm stressed and distracted, my confidence slips because I have to try to remember how long a similar situation took last time...

It's having too many things to do at once that normally hampers my salesmanship. The solution I am going to try in the next few weeks here is to try to hire back my old employee and try to actually make money with him this time. That will hopefully free me up a bit to put into practice all the other crucial elements to build a sucessful business.