I do it by reflex. But sometimes I seem to be helpful talking other people through it. Try chatting with a friend about wanting to think this way while stressed and asking them if they could talk you through it if you come to them. Role play a couple plausible scenarios where you would be unproductively upset with yourself and see if you think mopey!you would be persuaded.

Sometimes, I find it helpful to parody (in a warm, we're-sharing-a-joke way, not a cold, you're-being-an-idiot way) the idea that feeling bad could be helpful. "Let's sit here and feel bad together! Even if mopeyness falls off with the square of the distance, with two of us, we'll have a slightly larger range on our magical problem fixing field."

Obviously depends on your audience! Pick a funny image that the other person can recognize themself in and laugh fondly about. Riddikulus!