The real world is more fun than grumpy adults have ever told you.
Don't listen to people in their 40s who act like the best part of your life ends the minute you get your diploma. Is the real world all cotton candy and unicorn rides? No. But sometimes, misery loves company and recruits it too. When you start a new job there will inevitably be a group of people there who don't like their job and don't like being an adult. Avoid these people like the plague. They've bought into the cultural lie that a "job is just a job" and that you should only work for the weekend. Nonsense. Your job can be meaningful. Your weekdays can matter.
Your 20s are lonelier than you think they'll be.
They're glamorized in culture, presented as the time of your life. As you bingewatch an entire season of House of Cards on Netflix, you will wonder, Is every other person my age at an amazing party right now that I didn't know about? They're not. The truth is, when you leave college, you leave the tightest, largest concentration of people who are your age. Suddenly, you're scattered around the country and community won't involve walking out onto the quad. You'll have to fight for it. That's not failure, that's reality. Seek it out. It's not easy to make friends as an adult but it's definitely possible if you'll be brave.