It's normal to fall out of love with /anything/, IMO. I fell out of love with playing guitar - I moved to a new city over a year ago, and left my most expensive guitar in its case. Then last month, I bought a bass guitar (I'd always wanted one), fell in love with that, and started playing my guitars again.

I think it's natural to reach a plateau with whatever interests you, where you understand enough that the original challenge is gone, and/or you meet a new challenge that you can't overcome. Change something up, come at it from a different angle and you will probably regain your enthusiasm.

And can I just say, you are the first person I have ever heard say that 'talking to customers' is in any way 'fun'... :)