I think one of my favorite things about going to Paris was that I figured out the Metro!
I live in Utah, and up until the past few years we have not had the best public transit system. We do have trax trains now but I live so close to work and the city that I still do not take it much at all, and ours is very simple anyways. However, The Metro in Paris is very complex. Tons of trains, all different colors on the transit map. You have to know where you are going in order to choose the right route, this can include multiple Metro trains ~ I know it might seem like a simple thing but on the first day I almost had a meltdown thinking I knew what I was doing :) And a lady yelled across the tracks asking me where I needed to go, I was not in the right place and somehow she could tell. From then on I did not have any issues and got on the right trains to the right places ~ I felt a little bit proud that I had actually figured it out :) It may seem like such a small thing, but at that point in my life it was huge ~