Once two men came to sage who used to live in forest inside a small hut. They requested him to allow them to be his students. Sage asked them to come next day. Next day when they came, sage was holding two birds in his hands. He asked them to hold on to birds. Both men took one bird each in their hands. Now sage instructed them, "Go and kill bird you are holding but there is one condition.."Men asked, "What?"Sage replied, "You can only kill bird at a place where no one can see you when you kill that bird.."First man immediately went inside forest, little far from sage's hut and looked here and there. Man saw that there was no one around, so he went behind a tree and kill that bird and brought it back to sage. Another man took that bird and went very far away to a deserted place. Then he stopped to kill bird. Then while he was looking at bird to kill it, he thought, "When I kill this bird, it sees me and I also see it, this means two and third god is watching all this,but sage ordered to kill this bird when these is no one else.."After thinking all this, that man brought that bird back alive to the sage and said, "Mahatma ji..!! I could not find any place where no one sees because god is everywhere."Sage replied, "You are right.. you have passed this test and have right to get knowledge, you can come to me as my student."Saying this sage asked first one to leave as he was not fit to be his student. 
If we always remember that god is everywhere and he can see us even when we try to sin hiding from everyone else.. Then we can stop ourselves from doing wrong. 