We may wonder why it is necessary to contemplate sufferings such as birth, aging, sickness, and death, especially since we have already experienced the first and can do nothing to avoid the others. The reason is that by meditating on these sufferings we realize that the very nature of samsaric existence is suffering, and that until we escape from samsara, we will have to experience the same pains in life after life. This induces a strong wish to escape from samsara by abandoning its cause, self-grasping. If we want real freedom and real happiness, we must escape from samsara.
Geshe Kelsang Gyatso - “Introduction to Buddhism”