Are there some circumstances when you should continue to contribute? 

Yes.  If you are 90% through the investment term if will almost always be best to complete the plan. Yet if only 10% through the plan you may have a chance to get out before it is too late. Again this will need careful consideration and study to make sure you make the right decision in effect the second time around.

The amount you invest is also very important. I always ask client to think of a number that will not affect their life style in anyway. I.e start small!

I love it when I meet with clients in our reviews and when asked if they missed the money leaving their account, the reply with no I did not even miss it. This I feel is the correct answer. You can always increase after all, you normally cannot every decrease and see positive results.