I saw a few small kids running after a beautiful Multicolored butterfly. The small insect was flying in its own, mood swing, here and there. Children were chasing it happily. Two of them fell on the ground and got hurt. The next moment, they got up and again started running along with other children after the butterfly. No one could get it. Children were tired. Instead of running they  began to walk now. Butterfly also sat on a flower. 
A cunning child, from behind a big tree, made his way to the butterfly stealthily and caught it in his little palms. All were happy. A bottle was brought and poor insect, the butterfly was left in the bottle with a closed lid. The bottle was left on the bench besides a tree in the park. Children went home with an air of victory and satisfaction on their faces. 
After some time a matured  person reached there, saw this, and opened the lid. The butterfly flew away. Next day children returned to the park. Now they wanted to set the butterfly free because they got such instructions from their elders. They were explained, why it was unfair to cage any life. But the butterfly was not found in the bottle there and the children were stunned. 
Friends, now try to notice, rather recall, that this is the cycle of a human life. Every moment, everything is heading towards destruction. Everything is running speedly in the direction of it's end. Because,  according to the law of nature, everything that is born must die one day. Still, we are all running somewhere after some or the other thing. 
Children represents, we all human beings whereas the butterfly represents, worldly attractions. After a long chase and hard work of months and years we grab the thing that we were running for. We reach to the aim that we were following uptill now. Then with great satisfaction, we take rest, go to sleep,  without thinking that the action we have performed was rather good or bad and what would be the outcome of it in future. After some time when we realize the truth, we want to make a reform, but we find that the chance is gone. Therefore, think a lot before doing anywork. Once we shoot an arrow towards somebody, we can't bring the life back. Though shooting is in our hands  but bringing life is not. So whatever is in your hands is only an opportunity not your fundamental right. It's only an opportunity to make the most of it. It's only a chance, given by the Almighty God, to you, to perform some better action in the favor of people around you. It's a responsibility handed over to you. It's an examination to prove your ability. Therefore, it is necessary to recognize the opportunity well in time and make the most of it. We must remember that opportunity knocks once at the door. We should be grateful to the Almighty God for  providing us this opportunity, for selecting us to do that responsibility  We should be also grateful for every moment given to us like a boon to do something better in our life. We perform some or the other action every moment. So every moment in our life is a golden opportunity for bringing reform or better change. 
You might have read the poem in your childhood that "Time is an old Gypsy man that goes but comes not." It is our Karma that definitely comes back like an echo with a big interest added to it. This karma is performed every moment by us knowingly or unknowingly, physically, mentally or through speech. Again, I will say, think a lot before doing. Because the time in which you have performed Karma will  surely pass away not to come back but leaving traces  of your karma that will have to be paid in future.