My return to the gym

I finally returned to the gym yesterday and had a fabulous work out.  StairMaster at level 10 for 23 min then at level 13 for the last 7 min. I burned 340 calories and went 3 miles. Now why can't I run three miles? I am not ready to tackle running yet but hopefully this spring and summer I will be.  I want to enter a 5K run just to see if I can do it.  That is my goal for the end of the year. I had to do some readjustment of my goals recently. Especially after my setback. I think I put too much pressure on myself to get to a certain weight. I have been wary but thought I was ready to try it. And nope. I need to just go at my own pace. It really is not about that number on the scale but how you feel in your skin.  Hopefully that sinks into my brain. So tomorrow and then next week the full week of gym workouts and P90X do over. I do have to modify the workout so as that I am not too bored with it.