Congratulations! I suggest “The One Minute Sales Manager” to read...

That reminds me of an interesting book I read on the topic of sales " The Go-Giver." 

I'd like to add that you're lucky that you and your sales coordinator (manager?) have such a good relationship and that you value his help. Take advantage of that! Go out on joint sales calls as much he wants and you can. You'll learn a lot.

Another idea: start keeping some sort of journal where you can jot down notes from your calls every day. I am sure you do this but I'm talking about another notebook where you gradually build up your own system to visualize each sales call, especially those that aren't successful, where success means that you think you have a chance at an eventual sale. 

The reason is I say this is that long ago and in a faraway galaxy I was the first sales engineer hired to sell a new system for manufacturing printed circuit boards. Our system would optically scan the boards and (when it worked, it was a prototype when I started!) quickly identity flaws that saved the manufacturer lots of money. I was struggling big time. I was going door to door down through the list of companies who manufactured these boards and often got sort shrift from the GMs and owners. But then a man in our company who led our operations group wanted to take on a sales role to broaden his experience and eventually become a GM or executive himself. He did exactly what I'm suggesting to you now and quickly saw the commonalities about being rejected. Together (but mostly him) we developed a strategy that we had a blast with. We would call the prospect and say that all we needed was 60 seconds of his time (in a face to face meeting) to demonstrate on the back of an envelope how we could save him tens of thousands of dollars every year. We promised to set up a timer and if, at the end of the minute, he didn't want to continue, we'd shake hands and depart. Well, this really helped in two main ways: 1) We got the meeting, but more importantly 2) We had to boil down our benefits sufficiently into language he'd quickly grasp enough that he would want to learn more. I ended up selling way more machines than anyone else in our group!

And I had fun, too. We turned it into a game to see if our assumptions on the meetings worked and when they didn't we refined our messaging and tactics.