I think being 'in-love' is nothing more than a subconscious process of chemical attraction for the sake of reproduction. The genes of your organism want to reproduce themselves with the best available genetic material. But Sometimes these genes don't have our personal happiness in mind.

Baring this in mind, my advice is more of a scientific nature than from the belief in soul mates and other 'spiritual' concerns.

Assuming you're a female, first I'd check how genetically compatible you are with this man. For example, do you like the smell of his body odour on dirty t-shirts? If the smell positively repulses you, then you should be very, very concerned. This could indicate that your immune systems are not compatible, and there may be a very real possibility that you might not be able to stand this man at a later date.

Check this for more details.

Another genetic concern is if you've only known this man while on the pill. The pill blocks a woman's ability to discern genetic attraction. Women who go off the pill - like when trying to have a baby, can suddenly discover they cannot stand their partner. Once again I back up my claims with solid science:

http://www.scientificamerican.com/article/birth-control-pills-affect-womens-taste/

Assuming you are perfectly genetically compatible, and you love the smell of your man's sweaty t-shirts, but maybe your man is ordinary looking, or doesn't earn the most money, or eats with his mouth open or whatever factor exists that makes you uncertain: what kind of father will this man make? You could produce the best biological offspring possible, but if this man will neglect his fatherly duty by being actively involved in every area of your future children's lives, what's the use?

So to summarise: what kind of father will this man make? If you think he'd make a great father, you could be making a good choice.

My advice if you're a male is exactly the same: what kind of mother will this woman make. If you are a male though, and you find her sexually attractive, you probably don't have to worry about smelling her dirty t-shirts.