Dry firing practice is vital to grooving a solid, consistent grip and firing technique. I've found it useful to practice by aiming at translucent, fabric type lampshade when the lamp is lit. This will make the front and rear sights appear in a solid, clear, bold silhouette, and you can easily see every little quiver, deviation, dip in your sight alignment as you press the trigger. As Airacuda notes, I'll bet you find you're allowing the muzzle to dip, particularly at the instant the trigger releases, the hammer falls, and the dry fire "shot" releases. You can also easily see what happens to the sight alignment when you reflexively tighten the other fingers in your trigger hand sympathetically as you squeeze your trigger finger. Your trigger figure must move totally independently of the other fingers and thumb.
Remember, as others much more experienced than I have said: pulling the trigger and breaking the shot is a process not an event.