Some of you guys must be as fragile as porcelain dolls. Run until you're uncomfortable and keep running but not to where it's painful, thats the threshhold you want.
Run hills and integrate sprints into your runs, you burn more calories if you start out fast, though if you go all out sprinting there won't be much of a run left. Get good shoes fitted properly, you dont need all UA stuff, though I do, it's not necessary it's just what I prefer. If soaking cotton shirts is what you want, well you should join the army.
Anyways it's not hard, if you can't run or feel too tired, atleast walk the distance you were going to run to get the mileage. Slowly your body will make you want to run on the days you walk. Do daily doubles if you want, don't be a pansy like some of these guys on here, you're young at 23 you won't break yourself. Integrate swimming into your workout, it'll help you stretch out your muscles but also get your cardio up without the impact of the ground. It's really just getting off the couch and walking/running and not overdoing yourself.