I've been riding for just over two years now, and it was only after riding for 500+ miles using clipless pedals that I finally felt confident that I could clip in and out of them if I had to make a sudden stop. Part of the reason is experience and the other is my SPD pedals are worn enough that it's easier to clip in and out of them. Like everyone else I fell at least 4-5 times and bloodied and bruised my knees, elbows, ankles, and legs a few times learning how to use the clipless pedals. I actually thought about swapping them out for platform pedals, but we live in Seattle, and it's just so much easier climbing hills when you're clipped in.

These are the tips I wish someone had given me when I was first learning how to use them:

It's easier to clip out when your foot is at the bottom of the pedal stroke, but it's much easier to lean and step your foot down on the ground when your foot is at the top of the pedal stroke. That means 50-100 feet (or more) before you need to stop, clip your foot out when it's at the bottom of the pedal stroke, then rotate your pedals until your foot is at the top of the pedal stroke (unclipped), so when you stop and lean slightly towards the foot you're stepping down on, you can step down on that foot.

When you start moving again, it's easier to get going when one foot is clipped in, which is why I usually keep my right foot clipped it. It's easiest to get going when the foot that's clipped is at the top of the pedal stroke, so you can press down on that foot to start moving while you're trying to get the other foot clipped in. That means when you're stopped and your unclipped foot is on the ground, backpedal your clipped foot until it's at the top of the pedal stroke. When you're ready to start moving again, lean forward and press on the clipped foot to get going, then you can get your other foot clipped in while you're already moving.

Once you get more confident, you can decrease the distance between when you clip out and when you actually have to stop. Even now I'm more comfortable clipping in and out just my left shoe, and I only ever clip out my right shoe if I have to stop suddenly and I'm leaning right.

Just some ideas.