Devotions. From some private comments I got, I guess I over- and under-explained this one. At the same time!
When we Catholics say people have a devotion to some aspect of God, or some saint, or some useful practice, it basically means that they love it and they persevere in working with it. They’re devoted to it. They have a devotion.
Or… maybe I need an example. Okay, say you meet some people in a Precious Blood order, and shortly afterward, you come across that verse from Peter about the Precious Blood. You start thinking about that verse a lot, and its implications. You start running into other mentions of the Precious Blood, maybe find a book about it or a holy card. It starts to be one of the primary ways you meditate about salvation, and the more you get into it, the more you seem to understand what’s going on, and the more depths open up to you. Then maybe you learn a prayer about it, or find out what other people in the past were interested in this. Maybe you get some prayers granted, or maybe you just learn to carry your own cross a bit better. Probably you talk to people about Jesus’ Precious Blood whenever it comes up — and probably it comes up more often than you’d expect. After a while, you realize you’ve got a devotion to the Precious Blood.
Most Catholics at least have their favorites among the saints, or their favorite ways of looking at Jesus, whether or not they’d express it as rising to the level of having a devotion. Adoro’s a blogger who can tell you something about having a devotion: her family is devoted to St. Padre Pio, and she has a personal devotion to Our Lady of Perpetual Help.
As Adoro points out, there is a certain element of personal devotion that seems to be part of Providence and the mysterious unity of the Body of Christ. Sure, sometimes people just like something, for conscious or even frivolous reasons. Sometimes, though, a saint or an aspect of the faith seems to find you and haunt you, until you finally start paying attention to God’s obvious will in the matter. You discover that these things already had ties to you, or that a saint’s life parallels your own in ways you never knew. It turns out that a faith practice is exactly what you needed, or that it leads you to people who need your help. All this increases your affection, of course.
There are certain devotions that are more attractive to people at certain points in life. A pregnant woman will feel a lot closer to St. Gerard Majella than a little old lady whose kids are long grown, probably. It is very likely that certain devotions are provided and shown to us to help us grow, both in ways common to all Christians and in ways tailored to our own individual characters and experiences. But of course, a lot of what you get depends on what you give — how you dispose yourself properly to receive graces, trusting in God but not treating Him as a vending machine.
But personal devotions are always optional — additions to the Faith. You can drop them whenever you feel like it; nothing wrong with choosing to do something else, or focus your interests and affections elsewhere. (As long as you are still doing the stuff commanded by Jesus and His Church, that is!) Still, if God offers you extra help and graces, why wouldn’t you want to glom onto them, for as long as He chooses to help you that way?