"In a tightly clenched fist" is where your hand will be in a defensive shooting situation, and that is good. Good marksmanship is a thing to strive for, but in the second of crisis you will want to have a deathgrip on your gun, and fortunately that's the way Nature has built us. You should be spending time shooting your gun in the manner for which it was designed -- close-up, fast shooting while the physical responses are running at warp speed.
Assuming a proper stance, finding your front sight and putting it on target, giving the trigger a smooth, controlled stroke -- these are all good things, things that should be done -- but they take time. Now, if you practice A LOT, you can get to the point where all these things come very, very fast -- but still slower than the short, "throw-a-punch"-type shooting that you will need to execute in the vast majority of situations where you'll need to shoot or die. The LCP is just about the best tiny pistol for that kind of predicament.