People all over the world process loss differently. Every culture all over the world has a different way to approach death and its aftermath.
In some cultures there is a designated mourning time. Like in Hinduist, Islamic, Catholic and Jewish traditions. Elsewhere in the world people have traditions that center around celebrating life. Consider a fairly new development in South Africa: an 'after tears party' which is held after the funeral, when friends and family get together to drink, joke, focus on comforting each other and remembering the deceased with fondness. A similar tradition is found in Irish culture.
I do not think that the way mourning happens in the Netherlands, where I am from, is necessarily based on a religion or specific tradition. It is just something that is rooted in the attitude of the Dutch and in my family also based on mere practicality. But recently someone I care about made me question the way loss is approached.