I have an imaginary friend or "alter ego".
This imaginary person is kind, practical and does not over-think.
When I am worried about something, I tell this imaginary person and she says something cheerful like "Nothing to worry about, you and me will sort this out together easily"
Then when I think about the problem, I do it in the form of a dialog. Me the worrier, telling my fears to the imaginary optimist.
Since my thoughts are like a dialog, it stops them from spiralling out of control. I also find it very comforting (even though I fully understand this person is not real).