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There's another interesting quality of your "afternoon work": if you didn't do it, nobody else would. Paid work is by definition fungible: there's an economic demand for it, so logically if you don't do then somebody else will. Net benefit of your labor: zero! But when you work on some project from other motivations, you know that the marginal utility of your labor is 100%. Nobody's paying for it so it might never get done otherwise. It took me a while to grasp this but IMO it's an important latent motivation for volunteering.