Jerome Kern wrote, "When you're in love, smoke gets in your eyes." And that smoke can quickly turn into a smokescreen that you are unable to see through to see if your love relationship has any chance of lasting.
Before you say, "I do," or even "I will," you might do well to see if you and your partner have the capacity to like each other through thick and thin.
Difference of opinion -> disagreement -> argument -> fight -> ultimatums -> war -> game and relationship over.
One of the things you want to become aware of is how you as a couple deal with a difference of opinion. Couples with the best chance of success are those where a difference of opinion may escalate to a disagreement, but where it doesn't escalate further into an argument, then a fight, then ultimatums and then war.
Early on you may not experience this while your relationship is temporarily inoculated by the lingering smoke that got in your eyes when you fell in love. However, you can get a "smoke-free" preview of your relationship when you observe how your partner reacts to any of the following 10 situations where their true self comes out in their reactions:
Finally, you and your partner would do well to see if you both understand, agree and accept this definition of true love by Louis de Bernières:
Love is a temporary madness, it erupts like volcanoes and then subsides. And when it subsides, you have to make a decision. You have to work out whether your roots have so entwined together that it is inconceivable that you should ever part. Because this is what love is. Love is not breathlessness, it is not excitement, it is not the promulgation of promises of eternal passion, it is not the desire to mate every second minute of the day, it is not lying awake at night imagining that he is kissing every cranny of your body. No, don't blush, I am telling you some truths. That is just being "in love," which any fool can do. Love itself is what is left over when being in love has burned away, and this is both an art and a fortunate accident.