What happens the morning after? Will we get closer? Or will I feel like I just made a big mistake?

The “morning after” usually refers to what happens after two people have sex. It usually depends on what happens “the night before.” 
If you and your partner have talked about the decision to have sex, your experience together will be something you can discuss and be open about. And if you practice safer sex (like condoms and birth control), there’s a better chance of feeling OK about the experience after it happens.
Sex won’t automatically bring you closer. Knowing this, you’ll probably feel better if you and your partner agree on some important things beforehand. Why do you want to have sex? What does having sex mean to each of you? One might feel like it signals a committed relationship, the other might see it as just another experience that they want to have. Is this a one-time thing or something you expect to be part of your future with this person? Do you and your partner want the same things from the relationship? This is very important. If you want different things—one of you wants casual sex and the other wants a commitment—you may decide that sex isn’t the best thing for you to share.
It’s also important to talk about the possible outcomes of having sex—these include the emotions that come with having sex, pregnancy, sexually transmitted diseases including HIV. Does having sex fit with your values? What would you do if a pregnancy happened? How would you feel if you got an STD (sexually transmitted disease) or your partner got one from you? If you are a heterosexual couple, you want to think about preventing pregnancy as well as STDs. If you’re a lesbian or gay couple, you want to think about preventing STDs. What kinds of protection do you need to use? Who will buy the protection you need? What will you do if it fails?
For more information on getting contraception and preventing the transmission of STDs call 1-800-230-PLAN (7526) to be connected to a Planned Parenthood near you.