There are several versions of this story told in different cultures. The story is about a farmer who meets a genie, a fairy, or in the Irish version a leprechaun. In order to keep his crock of gold the leprechaun promises the farmer that he can keep all the land he can walk in a day, but with one proviso, that he has to be back to the point where he starts his walk by sundown.
The farmer thinks for a minute and plots a course which he knows will bring great reward. He starts his quest at a great pace and runs for miles to the west, taking in some beautiful pasture lands, he then heads south and takes in a vast forest, he is still moving well and is doing a fair pace, it is midday. Now he heads east, skirting a piece of land with good road frontage (he is an Irish farmer after all). He is getting tired and it is getting late in the afternoon, but his spirits are high thinking of all he will own. It is now time to be heading back to the start point as the sun is beginning to drop.
Not too far from the start point he remembers that there is a beautiful lake nearby that would be a huge benefit to him now that he has so much land on which to graze his cows. He decides the lake is worth the detour and off he goes. He skirts the lake and heads for the finish with the sun just about gone, however as he is pushing himself to get to the chosen point he hits a hole and twists his ankle badly. He cannot walk and despite his best efforts he does not make it back in time.
As he sits forlornly in the gloom, nursing his ankle and his broken heart, the leprechaun appears beside him. The leprechaun laughs at the farmer and tells him it was his greed that undid him.
At the outset the farmer had a plan, which would have given him great wealth, but in his greed he thought he could get more. How often do we allow ourselves to fall into the trap of extending a task beyond its initial objectives, to the detriment of those objectives. The Americans call it mission creep, in Ireland we might call it something else!