Thats great! Even the smallest break through makes me feel good and keeps me setting myself mini targets. Everytime you feel good, no aches, not out of breath, try setting yourself a target to go that little bit further. When you feel good make the most of it!
I have been trying to do an extra km everytime I feel like that, even if its a bit too much I feel great for doing any kind of personal best, even if its only a few yards!
My breakthrough moment was running around a lake near me, I'd tried it many times and never got close, when I made it I was happy for days!!