For want of a nail the shoe was lost,
for want of a shoe the horse was lost,
for want of a horse the knight was lost,
for want of a knight the battle was lost,
for want of a battle the kingdom was lost.
So a kingdom was lost—all for want of a nail.

This proverb has been around for, at least, 700 years.  It does an amazing job of projecting a visual of its message: seemingly minor details can have unforeseen and potentially grave consequences.  In this version of the proverb lacking one spare nail to hold on a horse shoe snowballed into an entire kingdom being destroyed.  While that may be a little far reaching, there can be no doubt that a small action or inaction can trigger a series of consequences that may have a powerful affect on the outcome.

All this talk of horses and knights may be a little dates.  A more modern version could be:

For want of calling a customer the sale was lost,
for want of a sale the client was lost,
for want of a client the month was lost,
for want of a month the quarter was lost,
for want of a quarter the business was lost.
So a business was lost—all for want of calling a customer .

Picking up the phone and making customer calls is frequently listed as one of the most difficult things for a salesperson or entrepreneur to do.  Unfortunately, every time a phone call isn’t made, it is like taking a nail away from the knight.  Perhaps this particular nail isn’t significant to the business but you will never know that.  By the way, emailing or messaging isn’t the same.