Hi Yen, When I first started on an SPD I felt once and vow that I will practice until I can unclip without even thinking. I bruised my knee cap and scraped a layer of skin.

The trick is to loosen up your spd clip. I found clipping and unclipping become easier as the cleat is more adaptive.

For one week when I first started on spd, i was clip only on one side. I practice unclipping on that side.

Now I have upgraded myself to speedplay cleats and thansk god I have not fallen. Don't give up!