Oh, ouch, ouch, ouch!! I've had two severe impingements and the last one last spring had me on narcotic pain drugs for a week. I agree with Meg's advice, and would add not to do anything like bowling, or lugging a heavy suitcase that pulls that joint apart and lets the end of the tendon slip in. The last one I had came from trying to reach something overhead and off to the side. I was standing on a stepladder awkwardly reaching and I felt it happen, but it was then too late.....
"Promise me you'll always remember: You're braver than you believe, and stronger than you seem, and smarter than you think." Christopher Robin to Pooh