Bddhism

1) Visit a grave “HAKAMAIRI”
2) Say “Itadakimasu and Gochisousama”
3) Eat OSECHI at New years day
4) Light up lantern for household Buddhist altar during OBON
5) Observe five seasonal festival for example March 3rd, May 5th and July 7th.

I don't know why we do these things. Because I had done them from my earliest recollection. However, I guess that reason Japanese has the custom of expressing gratitude for everything.