Stamina Workout.

Im going for a stamina workout today and quickly getting tired since that its been long i've never had it. My workout for today only take 1 hour as i can't proceed to go for the next lap. My stamina has got enough for 1 lap and i dunno how am i going to increase my stamina level the nextime im on it...PHEWWWW!!!!! By the way.... i already get tired before my muscles get a good workout lol!!!.
How would I gain more stamina to run longer without getting tired?Before starting that I walk quickly to warm up for a few minutes as to ensure my body's ability to perform workouts without getting tired so quickly. I AM GETTING TIRED SO QUICKLY NOW!!!!!. It was far more diff during my younger days. The only solutions is that i have to workout everyday to rebuild my stamina. Im not quite sure whether i can make it. That's about it.hehehe.

My workout time : 9:45am-10-45am (If im not mistaken).