It takes practice and the wave sure gets me sometimes, knocking me right into the surf.

Catching that wave when it begins is key. What happens, what thoughts and feelings are there when the overwhelming begins. I'm not saying it's easy to do, but it is something to work hard on so you can see what it's all about.
For example, it might start with feeling lonely, and thoughts about loneliness turn to despair because it seems like it will always be this way? You might want to write about it in a journal to help you remember, to look at and think about later.

Distraction can help by doing something that takes focusing, if you're able to do that. A book, tv, a hobby, a walk, a phone call to a friend...