The concept of vocation is important in Catholic spirituality. Much of it is dithering of the sort one can only be embarrassed to watch. For my own part, the idea of vocation is valuable in two very important ways, and worthless in its most commonly taken third sense.
1.) As a part of a general call to holiness. In this sense “discerning your vocation” means simply to focus on spiritual growth and to take it as a decisive and central, even including the important decision of what vows you should be taking. That said, every action in your life falls under this general call to holiness. You want God to be a part of your decisions about what vows you should take in much the same way that you want him to be a part of the decisions you make about anything: how you should act towards others, what you should do with your day, what movies you should watch, etc.
2.) As an account of vows one has already taken. Married persons must see their marriage as their vocation, simply by the fact that they were and are married. It is impossible that it is a mistake that must be dissolved or done away with. There are hard cases here, to be sure, but all vows in the Catholic sacramental dispensation are underwritten by omniscience, and omniscience cannot be mistaken or deceived. Absent this awareness, we might come to think that the vows we took were never meant to work out, or that it is blameless or even natural to “drift apart”, or that we’d be better off with someone else. This sense of vocation is crucial to me and, to be honest, I don’t see how anyone can make a vow without it.
But then there is the most common and worthless sense of the term
3.) The special revelation showing us what in particular we should do with our life. If, so we think, we just say the right prayer, recite the right formula or pay off the divinity with enough earnest and confused anxiety we will get some mystical assurance of what exactly to do with life. To be blunt, this has nothing to do with vow taking but is sheer superstition. All that ever comes of it is occasional emotional outpourings that are taken as surges of conviction followed by the anxiety of second guessing, morbid introspection, and endless questions that no one can answer – all of which add up to decade-sized units of wasted time.