1. When Ted finally meets Tracy.
2. When getting dumped at the altar turns out to be a good thing.
3. When Barney and Robin break up.
4. When Robin and Barney got back together.
5. When Tracy laughs at Ted's "shellfish" joke.
6. When Barney and Robin first have cigars and scotch together.
7. When Ted hears Tracy play "La Vie En Rose" for the first time.
8. When Ted finds Robin's locket.
9. When Lily and Marshall make new, more realistic vows.
Showing us that there are some promises that couples can keep forever.
10. When Robin and Barney lie to each other for their own good.
In this running motif throughout the series, the best example is when Barney constructs a series of elaborate lies leading up to his proposal to Robin. The important thing is that the love is true.
11. When Lily leaves Marshall, and then comes back.
12. When Marshall and Lily wear matching Halloween costumes and/or sweaters.
13. When Lily and Marshall pause their arguments.
Showing that no matter how serious a fight is, you have to be able to put your bad feelings aside and remember what's really important.
14. When Lily and Marshall decide to carry on their tradition of greeting each other at the airport (with a six-pack).
Reminding us how crucial it is to never stop doing little things to show each other you appreciate one another, no matter how much time passes.
15. When Ted asks Robin if she loves him and she says, "No."
16. When Ted shows up to Robin's doorstep with a blue French horn, 24 years after the first time.
17. When the place where Ted experiences his lowest moment...
...becomes the place where he experiences his highest.
18. When the fact that it took Ted so long to find Tracy just makes him appreciate her even more, until the very end.
19. When Ted has the life he always wanted with Tracy.
Proving that you should always wait for, it. Seriously, wait for it. Because you never know when you're going to meet someone who "hits the reset button on the world, who makes everything new again, who makes it seem ridiculous that you ever considered settling." And that's pretty legendary.