Few garments are off-balance on their own. The issue lies in proportions. A long jacket on top of a long shirt on top of long pants is still within the realm of matching, but the overall effect can make you look too long in every direction. Learning how different proportions work with each other is the first step to understanding your body. And the best way to understand proportion is to practice.
The best way to practice is to play dress up with a few articles of clothes. I recommend grabbing three shirts and two pants and nothing else. Forget about colors for now and focus on how they sit on your body. The difference between a shirt that hits the hip and a shirt that hits mid-thigh is immense. Try on all combinations and pay attention to the differences. Pay attention to when you can see your waist and when you can’t, when your torso looks longer and when your legs look longer.
One of the biggest mistakes people make when trying to balance proportions is attempting to divide their body in half. This typically results in a stagnant look because your eye always craves some variation. If your jacket ends where your pants begin, you end up looking like you’re wearing two blocks. Allow your shirt to peek out from underneath your jacket or your pants to sit higher on your waist to create some variation.
And, of course, don’t forget about texture. Different weights and weaves can greatly affect the silhouette. Structured garments will always create a harsher line than soft garments. If you combine too many structured garments, you will look boxy no matter how well-fitted your clothes are. One structured garment and softer garments will typically balance each other out. So if you want to wear a boxy jacket, allow a softer shirt to peek out from underneath instead of layering another structured garment underneath.