To sketch fashion designs, being patient is, for me, more important than being perfect. The hardest obstacle had by most beginners when they start making their first sketch is they push themselves too hard to be perfect.
In one side, pushing ourselves to be perfect is good to help us improving our skill. In the other side, it can be just stopping us to enjoy and free ourselves in creating a fashion sketch. A popular and professional fashion designer has spent years crafting their sketching skills. Otherwise, you can still have a chance to sketch as easy as to pick up a pencil and paper like a professional designer.
To sketch fashion designs, you should not be afraid of making mistakes. Every person can be trained to make a fashion sketch after all. If you want to sketch just like to pick up a pencil and paper, you have to be patient taking a lot of exercises for years. When you discover that your fashion sketch is not perfectly proportioned, you must not give up or even depressed because a fashion sketch must not really lifelike. The most important matter to sketch fashion designs is focusing more on capturing the feeling of your design.