Exercising is a lot more than a way to look pretty and stay healthy and fit. Working out results in having more energy, feeling happier, being more self-confident and in many more physical and mental benefits.
The most frequent feeling you get, however, during your training is “like you’re going to die.” Chances are that this is not going to happen and that you actually have a lot more energy to keep exercising. Realistically measuring how long you can go on depends on several factors such as heart rate, muscle fatigue, hunger, intensity.
A quality workout doesn’t have to be long at all despite what your ultimate goal is. Building muscle of losing weight is obtainable with 20-minute workouts as opposed to an hour at the gym (who has so much free time anyway…). Maintaining your weight doesn’t need a lot more than half an hour of brisk walk every day and eating right.