Settling the body only goes so far for some people, and there is energy left over afterwards. That leftover needs somewhere to go, or it goes back into the worry.

What the research says

In a controlled comparison against progressive muscle relaxation, a structured attention training exercise improved children's ability to hold off on an immediate reward, which suggests the gain came from training attention rather than from being relaxed. Where attention is pointed looks like a separate lever from how tense the body is. That was a study in children about a laboratory task, so read it as support for the principle rather than for any particular activity.

Strength of evidence: one line of research. A single study, or a theoretical account.