מעשה שהיה.....
Two fathers watched their 3 year old son and daughter playing together SO NICELY!! They decided that it would be a GREAT shidduch. So they took an oath that when the time came they will marry the two children to each other.
Well, the time came and neither the boy nor the girl were interested in marrying the other. What's good in the playground doesn't necessarily work for life.... Now the fathers were in a bind. On one hand they swore that there would be a shidduch and on the other hand the kids weren't interested.
Rav Elyashiv ztz"l was asked what to do and he replied that they don't have to get married and the fathers don't transgress the prohibition of swearing falsely. What the fathers really MEANT was that they would TRY to ensure that their kids marry each other but not that they would DEFINITELY do so.
Moral of the story: Be careful with your words:-).