Simeon had the promise but during his wait there must have been times that he grew tired or restless. Some may have pitied poor old Simeon, that guy wandering around the temple waiting for the Messiah in his lifetime. Note that he had no following; he wasn't recognized by the high priest.

All he had was the promise. And God answered it unexpectedly one day and made his joy and his life complete. Simeon's experience is a parable to teach us about our own experience God's promise to each of us:

That one day He will come, and in the twinkling of an eye we will all be changed and we will all be with Him in heaven rejoicing forever.
That promise will be fulfilled one day; probably in a way we can't imagine now, a way that will catch us off-guard.

So don't let the mocking, or the indifference of the world deter you from waiting patiently on your lord - He will come and you will be so happy that you waited.