Kids. Not because they cost alot of money, which they do... more because they demand energy and time. In our case it means it only makes sense for one of us to be working until school ages... which is obviously not ideal for savings rate.
This is why making as much progress as possible before ze children is obviously really helpful. They are awesome though =].
I was thinking of ways we "sabbotage" our retirement saving and money goals, and I , too, came up with kids. Not the having them, or raising them, but the strange things we let ourselves as parents believe we need to do so that they will get the "best possible start"... etc.
It is very easy to justify saving 10% and spending everything else so that the kids have the best opportunities in life.
I was sucked into this for a couple of years, so I escaped early. Others? Private school, expensive tutors or after school activities, clothes, living in a good school district when the "not good" one is actually pretty great and safe, saving $100k so they can go to an out of state private college, buying another car, it all adds up and so many parents rationalize it as "need" not a "want".
And then the exhausted parents are paying for household help and take out to just "get by", and buying love with fancy presents and vacations because they can't be there enough for kids during the week. (Guilt spending)
.....
Hmmm, maybe setting up a lack of boundaries with family about spending money, and the whole "guilt money" should be listed here, not just kids.....