One of the most important documents contained within your estate plan is the will. Your will dictates how your affairs, assets and property are dealt with in the wake of your passing. Without a will, you die "intestate," and your estate is then subject to all of the state laws that apply under the intestate status.
But a will is a very tricky document to truly feel is "finalized." Your feelings and opinions will shift over the years, and the lives of your heirs and beneficiaries will change too. After you write a will, life events may require you to return to the will and make revisions. This is perfectly fine -- but you need to follow the necessary steps to ensure those changes are applied correctly.
At the same time, changing your will can be a dicey proposition if someone has nefarious intentions. For example, some beneficiaries challenge a will that seemingly gives most of the assets to one person. Maybe that one person wielded some undue influence on the individual who's estate is in question because he or she was in a weakened or unhealthy state.
Another possible scenario is that the individual revoke's his or her own will to create another one. In this case, the first will no longer has any legal standing -- but it must be destroyed by the individual. The new will would apply, and all of the provisions contained within it.
Source: FindLaw, "Revoking, Challenging or Changing a Will," Accessed Jan. 28, 2016