Power switch breaks off when I put DS Lite back together?

My DS Lite power switch broke, so I bought a new one, fixed it back on, I checked it before putting the case back together and everything worked as it should, but when I put it all back together the new switch broke off again ( just the little black bit that sticks out ), I do have another new switch but just wondered if anybody had any tips on how to put it back together without it breaking again before I try again.

Here's hoping and thankyou in advance.