Question: > 
> Many an opportunity is lost because a man is out looking for four-leaf
>  clovers.
> 
> 
> 

I have no idea what the quotation means. Is there any special meaning about four-leaf clovers that I may be unaware of?

Answer: 
My guess is: success comes more from conscientiousness (seizing opportunities) than from luck (four-leaf clovers). Or: don't rely on luck, take advantage of opportunities.
It means valuable opportunities are easily squandered by spending too much time searching for things that are difficult (or impossible) to find. 

For example, chasing after a scholarship from NC State with single-minded intensity may cause someone to miss the fact that they've been already been accepted by ECU.

IDK if that helped; I hope it did. :)