I'm too dumb to say anything new or profound about the old "Free will vs. God's omniscience" debate, but I'm a blogger so I won't let that stop me. At the outset it's important to make a distinction between God's active will and God's permissive will. The final cause, or telos, of the universe is the glory of God and everything that happens is ordered toward that end. God gave human beings free will and we are to use our free will to choose the good and avoid the evil. Obviously we don't always do this. God does not will us to sin but he permits it and can draw good from it, e.g. the man who sins and suffers for it can come to realize that he is helpless by himself and that he must trust in God. So far so good.
God wills that all men be saved but it's clear from Scripture that not all men are saved. Is this the fault of God? No, it is the result of our free choice. If a man goes to hell it is, pardon the expression, his own damned fault. Therefore, it's a category error when atheists or pagans ask how a good and loving God could possibly sentence someone to burn in hell for all eternity. He doesn't; the damned chose their eternal destiny by turning away from the Good. Knowing this, why do we willfully sin? Hell if I know.
God created each individual with some purpose in mind. That's why we talk so much about "discerning God's will for our life." How much can we really know about it though? If we're immersed in a riotous, sinful lifestyle, it's unlikely the Almighty is going to whisper in our ears what He wants us to do. But even if we do everything right on our end - pray, receive the sacraments, live virtuously - He's not going to boom out His will for us from on high. Take a look at yourself while you're before the Blessed Sacrament.
What are you good at? Maybe you can sing, or write, or draw. Maybe you're good with numbers, or you're interested in science. Think in the broadest, most general terms first. Once you've figured out what you're good at, look at the different fields within that skill set: musician, author, artist, accounting, physicist, etc. You may be thinking that fields like science and mathematics and business or whatever are not appropriate for a religious outlook. On the contrary: everything is ordered to the glory of God whether we intend it or not. By being a good Catholic Christian, you are contributing to the glory of God whether you explicitly speak of your faith to your fellows or not.
If you, Catholic reader, are good at stringing a coherent sentence together, why not start a blog or write a novel or screenplay? It's a tough racket, sure, but today it's never been easier to publish something. Getting discovered by a wide audience, well, that's a different story. Keep at it though.