Information is infinite. Your ability to obtain and process it is finite. The more serious the decision, the less likely it is that you will have all the related information, even when you apply all effort possible to obtain it. However, by listing pros and cons, you can guarantee that the decisions you make are the best you can make, and this is what is required to feel confidence, peace, and contentment in spite of your imperfect knowledge.
Given your imperfect knowledge, you should anticipate situations where new information presents itself. This means that no decision should be final. This is a scary proposition for most people because most people derive fleeting security from illusory things such as past decisions. For example, people get married in part because of the security they find in someone saying “I do.” The problem is that some 75% of marriages end in divorce. By mere statistics, marriage is most likely not going to last, yet people pretend it will.
Jesus taught that we should not make oaths, but rather let our “communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil.” (Matthew 5:37) Why? Because our understanding of what benefits is guaranteed to change if we seek God, who will teach us a more accurate understanding of reality. This is why James said:
But above all things, my brethren, swear not, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea; and your nay, nay; lest ye fall into condemnation. (James 5:12)
Security does not come from human promises, no matter how sacred and inviolable they seem. God provides the one and only form of surety: strength of character. If you find someone who is trustworthy, their entire lives will provide an integral testament that they, like God, always do only those things that are for the benefit of the world (see 2 Nephi 26:24). While you won’t find a person who has the same amount of knowledge as God, it is possible to find a person who consistently makes decisions the same way, and anyone who does less than this is as unreliable as anyone else you come across, no matter how sure their promises seem. Jesus knew this during his mortal ministry, and it is why he would not lean on even his apparently most devoted disciples even during their most zealous display of worship (see John 2:25).
Understand that nothing is final. While no one says they think they know everything there is to know, almost everyone acts as if they do. If you believe that the decisions you’ve made are final and should never be reconsidered, you must also believe that you know all there is to know. If you don’t know all there is to know, you must also consider that there may exist sufficient information currently unknown to you that would change your mind.
There is always something more to know, and knowing more will always change how you see things. If you are learning and growing, it will not be infrequent for you to see something as good that you used to see as bad and vice versa. If you haven’t recently reconsidered your previous perspective on a major topic, chances are you have a lot to gain by becoming more open-minded and less sure of what you think you know.