To be able to sacrifice yourself if necessary for the best good of someone else? Sure, that may be the highest (but not the only) form of love. To sacrifice yourself at the drop of a hat? That'd just be stupidity. Anyone who would ask you to give up everything for them would not be asking for a reasonable proof of your love; they'd merely be abusing you.

For most people, killing yourself would just be a bad idea. There's no need for it, even if you were willing. It seems to me that for most of us, the way love shines through is in how we live with someone rather than whether we die for someone. Are you patient with someone even when you're exhausted and really don't want to put up with them? Then at that moment, you're showing love.

All IMHO, of course. :-)