The law is very clear. If you do not change your will within three months of divorce you will be deemed to have intended it to remain as it was. If you die and have left everything to your ex, in your "old" will, he/she will inherit.
Think about that! Is this what you want? His/her new wife or family might inherit. Three months is not a long time especially when one is not really thinking rationally. In these circumstances, treat this as urgent and consult your attorney.
Even if you are not married it is important to have a will. This document expresses your directions with regard to your very personal feelings and intentions about what should take place after your demise, (Horrible thought, but nothing is more certain than death!).
Most of us only get around to doing something about this when we have to go to hospital, fly or indulge in some sort of risky sport.