The Halachic Agenda

The Shel"a HaKadosh writes (שבועות צ) that one is not called a posek if he is strict in his rulings for other people when that is not the Halachic imperative; for himself he can be as strict as he wants. We seen in Berachos (4a) that it says that King Dovid's hands were filthy with blood in order to declare a woman ritually pure for her husband. It does not say to determine if she was pure or impure. He toiled to find a way in which she was undoubtedly Halachically pure and not God forbid declare her impure and unnecessarily cause people to refrain from marital relations, God forbid. Undoubtedly a posek must be careful not to give a ruling that will lead people to sin, but the point is that finding a leniency is much greater than being strict.
So, too, with all Halachic rulings, even for ones self. It is meritorious to be strict when there is room for strictness. But if there is no room for strictness, but he is being strict out of ignorance, but if he would learn and clarify the topic he would see that there is no room for strictness, and he is yet strict, he is a Chosid Shoteh.