A pretty face, sensual pleasure and open (at least at first) access to pussy makes many a fellow crazy. It's called projection, infatuation and desire for possession.
Do not plan marriage before age 30... even 33 is better. Date the gal at least three years immediately prior to any committment. Both of you need the time to understand each other's life motivations, goals, aspirations and how you fit, or not, together. Avoid fantasy at all costs as it is as hollow as the inside of a volleyball.
Certainly have a pre-nupital that defines not only financial aspects but also the expectations of the marriage. This won't guarantee avoidance of any change of mind but does represent each one's committment to each other. If you cannot write it down for each other, get the hell away. Maybe not so romantic on the surface, but adds reality to the marriage vows one undertakes, and, if you really think about it... it is an honest heart thing for both to each other.