Everything has a reason. That reason may be beyond our current comprehension, however it's there.

And why would you be grateful for being alive? You didn't ask for it. I would have been perfectly content carrying on as I was before my conception.

If God is the one who gave you life surely he has some ulterior motive for you. And it's a leap of faith to think that the only way you can be grateful for your life is through accepting Jesus as your savior. I personally think that you are a lot more grateful for your life if you are going out and helping people, educating people, nurturing the environment, or anything of that sort as opposed to sitting in a building worshiping God even if God does exist.