Marksmanship is the basis of all armed (firearms) self defense. I matters little what gun, caliber or how may bullets you send in the direction of a target if they do not impact in the right place. Quantity and speed will never make up for accuracy and accuracy is born out of solid basic techniques and practicing fundamentals.
Every shot in your practice session needs to matter and should be executed as if it was the only round of ammo you are shooting that day. It has to land where you intended it to land. Otherwise you are just learning and ingraining bad habits that will be MUCH tougher to break as time goes by.
A good practice session should include at least 10-20 rounds of precise, accurate shots to warm up. This will focus your attention on the fundamentals and will allow you to move on to the more instinctive shooting exercises in your self defense range session.
Speed is not essential to the learning process. It is a product of learning, practice, experience and familiarity. Slow is smooth and smooth is fast... Do not rush, do it right, speed will come naturally!!!
Over 30 years of firearms instruction to civilians and Law Enforcement Officials. Over 16 years as a moderator on the world famous Guns & Ammo Magazine Forums