Defending vs. stronger neighbor early attacks

[Reverend Zombie]

I have been running into this situation in a few of my first MP games on crowded maps. The following comment came from the "problems with the tuatha" thread:

Well Pillin, better luck next time, and don't attack in turn four - you can't be ready to meat my religious mad men at that time, especially not when your men are'nt either religious or well protected

This raises a question that I as a new player have thought about. While it may be good advice not to attack a player who is stronger when you are unprepared, how do you deal with an earlier attack by your stronger neighbor?

Running up against Jotunheim early can be particularly scary.

What advice can vets offer for newer players such as myself to defend against early more powerful neighbors who choose to be agressive, without crippling the crucial starting expansion?