It's tempting to skip the warm-up and go straight into the main part of a workout, especially when time is limited. But the few minutes spent easing into and out of exercise often make the rest of the session more comfortable and more consistent, which matters more over months of training than any single workout does on its own. Skipping this step regularly is one of the more common reasons a workout starts to feel harder than it needs to.
A warm-up gradually raises heart rate, increases blood flow to the muscles being used, and gives joints a chance to move through their range of motion before being asked to work harder. Starting a workout at full effort, particularly after a day of sitting, can feel noticeably harder and less controlled than starting after a brief period of lighter movement, and that difference in how a session feels can influence whether a person looks forward to the next one.
A warm-up doesn't need to be long or elaborate to be useful. Five to ten minutes of light cardio, such as walking or easy cycling, combined with a few dynamic movements that mimic the upcoming workout, is usually enough to feel noticeably more prepared.
Ending a workout abruptly and moving straight to sitting down skips the chance to bring the heart rate back down gradually and to stretch muscles while they're still warm. A short cool-down of light movement followed by a few minutes of stretching can also serve as a natural signal that the workout is over, which some people find helpful for mentally transitioning out of exercise mode.
Neither a warm-up nor a cool-down needs to take much time to be worthwhile. Building both into the start and end of every session, even briefly, is one of the simpler habits that tends to make workouts feel more comfortable and sustainable over time.