HN user
In addition to what et-al said, the d3 wiki [1] has a list of tutorials. If you're looking for a book, I found Scott Murray's "Interactive Data Visualization for the Web" [2] to be good.
[1] https://github.com/d3/d3/wiki/Tutorials [2] http://alignedleft.com/work/d3-book-2e
I can only speak for Roman Catholicism. The only required Lenten restrictions are abstaining from meat on Fridays and fasting on Ash Wednesday and Good Friday. These restrictions are for everyone (apart from age and health exceptions).
Traditionally, Catholics choose to do additional self-discipline during Lent. The big three things that the Catholic Church encourages are increases in prayer, fasting, and almsgiving. The fasting part is where people often give up some type of food or drink, like coffee.
So the practice of giving up a personally-selected thing is not required, but it is encouraged and traditionally done as a way to come closer to God and prepare for Easter.