Why are some days "Hard Press Days" and some "Easy Press days"? I've always thought it has to do with barometric pressure and even thought of making an Excel sheet to figure it out, but I always forget once I have my nice Aeropress coffee in hand. ;) – From Kae E.

The more coffee and/or the finer the grind, the more important it is that you press gently.  Because pressing hard (even briefly) will compact the coffee and block the flow.  So always press gently and be patient.  It might take 60 seconds or longer.