(Don't look at the link or at the post at all, if you don't want to see American Beauty ruined before of having seen it)
http://www.youtube.com/watch?v=VGiI-MuTWf0
I just pick up one of my favourite scene of the movie in order to make you see my point.
About Heidegger of course his theories are too various and too difficult to understand for how he wrote them that probably that mention needs to be specificated:
(I know that it is absolutely incomplete, but right now I don't have the time to summarize properly all his thinking)
1) The fact that nothing is objectively right or wrong leads to a world in wich humans are gods (Nietzche's theory that Heidegger has made perfect)
2) Not only super humans can give Sense and Significance to things and to their lifes, but this process is made by every person, even if they don't know it.
3) But with the aknowledge of it, tasting the Happiness is truly possible, because we realize that every istant of our life is incredibly important, because whatever we will do, it will have Sense and Significance.
When he died he realizes and makes explicit this very last concept.
By the way this idea is far too complex to explain it in English so I don't think of being able to give further explanations of it:(