history: Impressed at my endurance after working out. Today I was quite impressed with my endurance during my work out. A few months ago_comma_ I couldn't even walk up a flight of stairs without losing my breath.
current: Sound like you're making a lot of progress!
next: I sure have, but it's such hard work. I make sure to work out, even on the days that I don't want to. It's definitely taken a lot of will power.