Watch the Picking Considerations 1 online guitar lesson by Bruce Arnold from Guitar Physiology Survival Guide
Picking too deep, which is also usually associated with picking too hard into the strings, will slow you down. You need to pick in as small of an arc as possible. As you move towards this position you will see that your volume decreases, but the tone gets better.
I've often had guitarists with bad technique pick up my guitar to sit in on a gig only to have people complain that they are too loud. In truth they haven't changed the volume they're just digging in too much. Also, by over picking you end up with a super messy sound as the pick pushes the string into other frets. Here's a simple thing to do to foster a light picking touch. Turn your amp up loud so that you have to pick softer. Now remember, that doesn't mean you can blast the neighbors.