One of the most important things to remember about infant care is: don’t change diapers in midstream.

Cast as mock “infant care” advice, the line is really a comic warning against meddling with a process while it is actively underway. The diaper-changing image turns a general principle—don’t interrupt something at its most volatile moment—into a vivid, slightly indelicate joke, typical of Don Marquis’s newspaper-humor sensibility. Read broadly, it cautions against premature intervention in politics, projects, or personal affairs: wait for a natural pause before making adjustments, because mid-course corrections can be messier than the original problem. The humor softens the admonition while making it memorable.