In פרק ד of this week's פרשה, it discusses the requirements of people or groups of people who sin inadvertently. A question is asked: Why should a person be punished for a sin he did not know he was doing? The answer is that there is hardly any such thing as a completely "inadvertent accident". While it is difficult to avoid all sins, you can attempt to do this by keeping yourself out of a situation that may result in your committing a sin, even if it was an accident. For example, if there is a light switch on a wall, you should avoid leaning on that wall on שבת since there is always a chance that you may accidentally hit the light switch. If we make it important to be sure we do not sin and take initiative to be sure we do not put ourselves in any situations where we might sin, the chances of committing an inadvertent sin will decrease. If we do not do our best to prevent these situations, it would mean that not committing these sins is not really important to us (see Rambam to ויקרא ד:א).
In פרק ד פסוק ב it says נפש כי יחטא בשגגה מכל מצות ה' אשר לא תעשינה, "If a person sins inadvertently by doing a negative commandment". This פסוק is commonly explained to mean that a person must atone for a sin that he has committed. However many Chassidic masters interpret this פסוק to mean that one must atone for failing to perform a מצוה without the proper intensity. They did תשבוה not only for the sins that they committed, but also for how they lacked the right כוונה in many of the מצוות that they performed. One student of the בעל שם טוב once said that when he dies, he will be more embarrassed to face Hashem and talk about the מצוות that he performed carelessly, than he would be to explain his sins.