A couple of excellent posts that pair well together:
Therefore, if you have sex outside marriage, you will have to steel yourself against sex’s power to soften your heart toward another person and make you more trusting. The problem is that, eventually, sex will lose its covenant-making power for you, even if you one day do get married. Ironically, then, sex outside of marriage eventually works backwards, making you less able to commit and trust another person.
You aren’t a real man until you’ve made a promise that could kill you. You don’t know what danger is, you haven’t faced a real adventure until you put everything on the line and risked it all.