Another interesting fact, that I unearthed from my notes was the difference between the promise and the contract. The basic difference is, that in promise, there is no institution behind it, so there are no explicit penalties. While in the contract, there is an institution behind it, so there are explicit penalties hardwired in.
So, dating would be a promise, since breaking it would have no explicit penalties. Sure, the partner can leave you, and the society can condemn you, but none of this is certain, and there is nobody and nothing that will make sure this happens.
On the other hand, in marriage, there are consequences. For example, apparently being unfaithful is illegal (though prostitution doesn't count, for some reason). Getting out of the marriage involved the legal process of separation, which can take a long time, since everything needs to be settled there.
This reminds me a bit of the contracts in the queerplatonic relationships community. Here is one explanation of a contract and something that people can use to make it more explicit. But because these don't have penalties written in, this means that they are more like a promise, and not a contract.
But even with promises, there is pasta sunt servanda, which means, that we are still obliged to fulfill promises, expect if all participants consent to not doing it or it becomes against the law.