Yep, discernment is like trying on clothing. A few weeks ago I went into a trendy men's store to buy a new pair of jeans. Let me tell you, it is really hard to find a pair of loose fitting jeans! I found myself in the fitting room, grunting as I tried to squeeeeeeeeze into this pair of stupidly tight jeans! Finally, after much maneuvering, twisting and breath-holding I got them on, looked in the mirror and they seemed to fit well...as long as I didn't make a single move. I was sure that if I dared to breathe out they would split, rip, pop and tear. I quickly changed out of them and decided it wasn't worth wearing trendy jeans if all I could do in them was stand still and suck my gut in!
Discernment can be a bit like this process. Discernment is learning about a vocation and beginning to "clothe" yourself in that vocation. Now here's the fun part of discernment you can choose to just stand there in the mirror checking how it all fits, asking if your butt looks big in this vocation or you can move around, stretch bend and see how it all fits. It'll either become obvious that it's not the right fit and you should try something else on or that it's the perfect fit and you should buy two pairs of those jeans (at least that's what the store assistant will tell you!)
If you really want to discern your vocation than take a courageous step and give it a good go. Try it on and move around in it. That's what my seminary and Canali House experiences were for me - a chance to see how priesthood fit (or more precisely, see how I fit into priesthood).
I believe God has a perfect vocational fit for each of us - how will you know yours unless you really try it on?