Your personality and thoughts are not born as they are, but intricately formed in many ways. As the saying goes, "One takes the behavior of one's company." Hanging around with positive-minded people will fill you with blossoms of happiness, which is infectious, as you may sometimes experience. Put it in opposite terms, if you are hanging around with negative-minded people most of the time, their negativity can, very likely, spoil your mind the way positivity fuels your motivation. The devils of negativity is contagious like yawning, no matter you like it or not. You may be a happy person in your blood, but can you be cleared of the harmful effects from others upon you, if you are repeatedly exposed to negativity? Probably not. The harmful effects from negativity seem slight at first, but only in the beginning. The more you are exposed to negativity, the more you will be negatively affected.