I agree with everything said... To add:
I've been married 4 years since May 16th.
What I have learned about "being married" and the "marriage" that I wish I known before: the money: His, yours and "ours" like REE said, it is wise to see a financial advisor too. That helped us tremendously. Financial goals are important for big ticket items: house, furnishings, children, etc.
The other thing like someone else pointed out is "in laws". You don't have to be their
very best friend and you can never prove yourself to them if they do not appreciate you already... The point is, your spouse is the ONLY opinion that matters...
And if you have some difficulty, or bumps along the way like everyone does in various ways:
Please read John Gottman books before you run away. And I personally like Gary Chapman. You realize that everyone had tough marriages at some point. But what makes it lasting seems to be folks attitude with one another grounded in love.
You never know how naked and vunerable you are until you are married... If you marry a good man, which I hope so, he will uplift you beyond all insecurities.
Have a wonderful wedding and a great marriage!