Most time we take decision without been cautious of its consequences and tends to affect us in the longrun;especially things that has to do with relationship thus,a little tips for you.
1. You must not get married
because of lust.
2. Infatuation (Love at first sight- sudden love)
3. Just liking the idea of
marriage. It's just like
joining the Army because you
like the uniform
Nobody joins the army with a promise that he
won't go to war.
4. The fear of remaining
unmarried(my
friends are all married).

It may be elusive to completely divorce lust from love.
Again, what you mean by sudden love is imprecise. Example, I met a girl yesterday at the cybercafe, they were discussing some issues. I was listening and watching her from afar.
I was attracted particularly by her disposition and demeanour which she betrayed in the cousre of the discussion and when what she wanted to do became problematic.
I wanted to ignore her, but couldnt restrain myself from commending her behaviour and later collecting her number. I will still call her...