Practicing to be a cranky old man

One of curious pleasures of getting older is that I become more and more optimistic, about life, the world, everything. However, this is not as it should be. Men my age tend to become cranky, realising that they are actually mortal. So what should I do? I am pondering the need to practice becoming a cranky old man. They say you need practice something new only for a month before it becomes a habit.