This. I don't regret the time I spend just thinking. I do however regret the time lost to boredom. They're not the same thing. Boredom to me is a state of wanting to do something but either not being able to or not knowing what that something is.
In one sense, it's the ability to accept an answer of 'unknown'. Maybe it's the ability to choose not to drive towards closure.
Maybe it's just being comfortable watching yourself get bored.