I am fit.... or am I?

So, I was walking up to my friend's third floor apartment today and felt a little winded when I got up to the top. Not the wheezy feeling, just the increased heart rate feeling. I thought to myself, "What the heck? I teach spin classes twice a week." The problem with that mentality is that just because I teach doesn't mean I'm in tip top shape. I actually can't push myself as hard because I have to be able to speak clearly to the class. So, I think I'm going to need to up my workouts when I'm by myself to make sure that I'm training hard enough.