When Ekalayva come to his guru to show the skills acquired considering him as Guru. Dronacharya feels jealous of his excellence. He asks for the thumb of right hand as gurudakshina. Ekalayva cuts his right thumb and produces in front of his Guru. All the skills learnt went futile because of absence of right thumb.
Now, in second world, Guru like Dronacharya asked for the Right hand, Ekalavya offered right thumb to Dronacharya. As Guru turned back, One arrow speeding towards Dronacharya makes bulls eye of his ear. Bleeding Dronacharya asked his Ekalavya how this happened, even you cut your right thumb..? Ekalavya answered,” I thought like previous Dronacharya you will ask right hand, So I have acquired astute skills with left hand. After offering gurudakshina to you, I took revenge you your cruelty”.
But, now in Kaliyuga, Dronacharya also learnt from this incidence. When Ekalavya come to Dronacharya, he ask for left thumb. Ekalavya scared, starts trembling. After some moments thinking “What to do..now.?” He prays to Lord Krishna, whispering some hymns.
After some moments Lord Krishna appears in the sky and tells, “Vatssa, Some time knowledge becomes inappropriate with certain time. So you must be flexible to work at all conditions. Dexterousness is character of human excellence. You must have to be skilled with left as well as right hand.”
Moral of the story is you should be excellent to work at different time and capability constraints. Multitasking is capacity to do number of work at a time.