All great points. I'll just on and add some more:
Life is risky and the only thing certain is that things will change. Even if you do nothing at all - even if you make no choices - things will change around you, so if you love this guy and you do want to marry him, you have to tell your fear to go fuck itself.
If it's the divorce stats you're worried about, don't be. Here's an article debunking the most egregious that might make you feel better: http://www.huffingtonpost.com/2011/01/07/divorce-myths-debunked_n_804934.html#s219156title=Half20of20All20Marriages20End20in20Divorce
I'll C+P the big myths for you:
In her guide to marriage, For Better, Tara Parker-Pope writes that since the 1970s, "marital stability appears to be improving each decade.” According to research at the University of Pennsylvania,* age is one of the clearest predictions of divorce.* 81% of college graduates who got married in the 1980s at age 26 or older were still married 20 years later, compared with 65% of college grads who got hitched before their 26th birthdays.
The Divorce Rate Is Rising According to the National Marriage Project, affluent Americans are enjoying increasingly stable marriages, while the divorce rate is rising among those without a college degree. An editorial by University of Pennsylvania professors in the New York Times suggests that the divorce rate has been falling continuously over the 25 years; it is at its lowest level since 1970. The marriage rate—though it’s declining—also indicates that marriages today are more stable than they once were.
Living Together Before Marriage Reduces the Chances of Divorce Today, “the nature of cohabitation has changed,” said Jay Teachman, a sociology professor at Western Washington University in Bellingham. Teachman’s research, published in 2003, indicates that a woman who has lived with only her future spouse faces no greater risk of divorce, but a woman who lived with someone else in addition to the eventual husband faced a higher likelihood of divorce.