When people would sneeze in ancient Rome, the above phrase was invoked to drive away the sign of illness, meaning usually an outbreak of plague. (Lit. Let the sign of illness be absent.)
Lent has its own omens of ill fortune as well. I set my alarm clock last night in the hope of saying part of the Divine Office before my Ash Wednesday Mass at 7:00 a.m. When the radio alarm started ringing and playing music, I looked at the clock. It read "6:30." That's when the fuzzzzzy thinking started. "Wait, that's not right...if it's 6:30, OH, NO..." I leapt out of bed, a sight to behold, skipped shower and tooth brushing (yes, the distribution of ashes was extra penitential this morning), and booked it over for Mass. Of course, everything went off fine.
Here's hoping that your Lent is already better than mine has been. I'm off for a shower.