["I had a great day at work today!  We are working on some pretty complex accounting, and I've had to do a lot of prep at night.", "That's really awesome, what makes it so complex?", "There are many different variables that need to be taken into account-- things that I don't usually deal with on a day to day basis.  But my extra prep at night has made it so that it's seeming easy."]
Well that's really great that you were able to prepare so much, obviously you know what you're doing! Do you usually have to prep so much?
I had a great day at work today; I really killed it!