Marriage is suppose to be a lifetime commitment. It's natural to want to (make sure) if whom you are with is someone you can imagine spending the rest of your life with.
In my opinion the #1 cause for divorce is marrying the wrong person for oneself. The #2 cause is getting married for the wrong reasons.
The first happens when a person hasn't figured out (who they are), what they want, and need in a mate for life. That's the equivalent of going shopping without a list! Such people are prone to allowing "happenstance" and "impulsive connections" to dictate their relationship choices.
The second occurs when a person has an "age goal", all of their friends are married, they're simply tired of being single, an ultimatum was given, an unplanned pregnancy, parental pressure, perspective mate has money, or someone in the military is about to depart and wants to have a person waiting. A marriage based around circumstances is likely to fail.
Marriage is just (one aspect) of a person's life. They have to consider all of their goals and whether or not the person they love supports them. In the end we're either growing together or growing apart.
The goal is to find someone who shares your same values, wants the same things for the marriage that you do, naturally agrees with you on how to obtain those things, and last but not least there is a mutual depth of love and desire for one another.
Never separate your mind from your heart when making relationship decisions. The purpose of the mind is to protect the heart.
One wants to enter into marriage with complete awareness and having realistic expectations! Not hoping for a "fairytale ending".
Second thoughts are red flag warnings not to be ignored.