How do I handle this without being a jerk?

I’m in a therapy group. I like the people there except that they can ramble on about things that aren’t therapeutic or relevant. Even the group therapist joins in with them. I get bored and impatient because we’re all paying for the therapy but they’re constantly digressing.

When this happens, how can I get our group back on track without sounding like a jerk or a control freak?