You might have heard how Russians ask a person who is in a bad mood the following sentence: “Ты что, не с той ноги встал?” (What's with you? Did you get out of the wrong side of the bed?).
In ancient times, people believed that the guardian angel always stands on the right side of a man's shoulder, and the left side on the shoulder was the place of the devil, who is always trying to do harm. Therefore, getting up in the morning on the right foot will make our day pretty good, while starting the day, with your left foot on the floor first, you will get trap into the devil's web.
In connection to this expression, it is believed that the words “правый” (right) and “правильный” (right, correct) have the same roots, and that the word “правый” (right) can be synonymous with the word “добрый” (kind, good). For example “это правильно” (that's right) and “правое дело” (the right thing).
And also, you might have noticed that in Russia, people spit over their left shoulder, usually three times, when they set about a new project, or when they talk about an existing one which works well. By spitting over their left shoulder, they actually spit into the devil's face, so he won't mess up with their business.
You might have heard how Russians ask a person who is in a bad mood the following sentence: What is with you? Did you get out of the wrong side of the bed?