…the origin of thinking is some perplexity, confusion, or doubt. Thinking is not a case of spontaneous combustion; it does not occur just on "general principles." There is something specific which occasions and evokes it. (Dewey 2010, p 1) ...the content of mind-wandering is predominantly future-focused … [and] frequently involves autobiographical planning (Baird et al, 2011, p1604).
Dealing with “perplexity, confusion or doubt” may take the form of planning, problem-solving, rehearsing, re-playing prior interactions (to reduce uncertainty on how to interpret the experience; or to reinforce an initial impression) and rumination. Since dealing with unfinished business involves contemplation of something not yet in its ideal state, a certain amount of mild negativity may be part of the process. For example, competent planning for just about anything requires consideration of what might go wrong. It stands to reason that when the mind is churning over unresolved issues, one’s hedonic states will be somewhat less enjoyable than, say, a flow experience, where attention is buoyed by a challenging but doable activity. Not a tragedy.
Dewey, John "What is thought?" Chapter 1 in How we think. Lexington, Mass: D.C. Heath, (1910): 1-13. https://www.brocku.ca/MeadProject/Dewey/Dewey_1910a/Dewey_1910_a.html
Baird, B., Smallwood, J. Schooler, and J. W. Back to the future: Autobiographical planning and the functionality of mind-wandering. Consciousness and Cognition 20 (2011) 1604–1611