Recently someone on a message board I frequent posted the metaphor that trying to convert someone (to christianity, in this case) was like throwing a life-preserver to a drowning man...
To Quote:
"If a friend of yours was drowning, wouldn't you want to throw a life-preserver out at them, or would you watch them drown? This is probably how your friend feels about you." ~BlueGuru
I felt it was more akin to the following:
A friend of yours is going on a cruise. Do you wish them a happy trip or do you try to force them to wear a life perserver?
To extend the analogy- your friend already knows that with any cruise there's the chance that the ship might sink and that there is a risk of drowning... however your friend has concientiously investigated the matter and knows that the chances of such an event are negligable... your friend also knows that the ship could just as easily be sacked by pirates or attacked by a giant squid... in which case an life-preserver would be useless.