ask …
a) Do I know the needs? What am I doing to determine the needs?
b) What decisions have I made so far, am I making now, and do I need to make in order to connect this lesson with those needs?"
Avoid the habit of assuming, just because you “covered” something, that that is enough. Whatever else student-centered-ness might mean, at the very least, we should all be able to agree that it means seeking tangible proof of what the kids are getting out of what you are doing.
The "better to have loved and lost" rationale really doesn't apply to attempts to execute pair work and group work activities correctly. There is a lot of other very meaningful work that you can do with the students. Do pair work only if you think it's likely to succeed.