Thanks for your quick answers
It helps me to understand more about hindu religion (that I don't know at all), their true rituals and separate them of the parents' saying.
Could you please tell me from where does this litterature comes : Somakanta said, [...] of one's dealings.
I like when you say that it has no link with superstition, because in the case of his parents, they are very superstitious : If he doesn't do ganesh chaturti, "he will never be happy and satisfied with life and God will punish him".
I think that all hindu ritual have a sense. This sense is often forgotten in some low educated places in india. The consequence is that people do these rituals because if they don't, they think something bad will happened. It is superstition more than religion or faith.
For example I have heard that during ganesh chaturti, you have to throw some water downstair before eating on a leaf downstair.
This is due to the fact that before, in old houses, if you eat downstair on a leaf, sometimes, hunts could come on your leaf.
To avoid that, people used to throw some water all around the leaf.
Today all people do not know the reason of throwing water, but they still
practice only because if they don't, they think they will get punished by god. This is a non sense.
I am looking for a book that would explain the reason of rituals so that to stop some superstitions.