answer:Really, it just takes time and effort. I was at a point of briskly walking, with sprint intervals, for about 2½ miles, 4 or 5 days a week for several months. I fell off the exercise wagon with a deafening thud about 5 months ago and am struggling to get back on. I’ve been sort of back at it for two weeks and the last two times I’ve found that I can (and want!) to go a little longer than the week before. Try this: Figure out how long you can go fairly comfortably right now. Do that 4 to 6 days for a week. The following week, add 5 minutes and see how you feel. Try it for a week. You may find that you can do more than 5 minutes longer, but don’t kill yourself doing it. I’m not saying to be a wimp, but you don’t want to make it so outrageously painful that you lose your motivation and stop! Keep adding time and/or distance as you gain stamina. It worked for me. I started walking for 15 minutes a day (I’m 5’1” and weighed 203 at that time.) and then started adding more to it. You can do this! Now I just have to follow my own advice. ugh!