Some clarifications need to be made. I don’t oppose to think, even think very thoughtfully when necessary in love. As a matter of fact, whatever we’re thinking or feeling types, our brain never stops thinking. The problem is people like INTJs or INTPs usually thinking too much. It’s unnecessary and definitely kills romance. Besides, they’re usually thinking about themselves and the future. Note this is not selfishness.
I’m not suggesting you shouldn’t be cautious. In English, people often use “guard your heart” to express the same meaning. However, “guard your heart” is to put yourself in an unconscious state of defense. The assumption behind this is that you will be hurt, or at least you may be hurt now or in the future. That’s reason why you would need to guard in the first place. Sooner or later, you let your guard down gradually, and completely succumb to their charm. Most people act like this way; when and how you let your guard down depend on your perception of their seriousness and sincerity.
That’s probably why many of love stories wind up with the heartbroken. Only will changing your mindset increase your chance of success in love.