Why does it say "Esperem me'Chol"?
Rashi: If I came to count [Tzadikim's] good deeds, they would exceed the sand of the sea.
Radak: When I come to count [Your thoughts], I cannot, for they are more than the sand of the sea.
What is the meaning of "Hekitzosi v'Odi Imach"?
Rashi: I came now to the Ketz (end) of the generations that You allotted until today, and still this generation is with You, in fear of You. I (the generation) did not veer from You.
Radak #1: Amidst my great thoughts about them, I dream about them while sleeping, and when I waken, I find myself with You, i.e. in thoughts of Your wonders.
Radak #2: [Even] if I were always awake - for man sleeps half his life - [rather,] I would be with You always, and not die - I could not count [Your thoughts].
Radak citing Ibn Ezra: When I think to know Your thoughts, it is like a Divine sight. The body lies, with its Neshamah clinging to the supreme Neshamah. Then it sees wondrous images, for this is unlike dreams.
Malbim: I feel like an independent intellect attached to physicality, and separate from Hashem - but after investigation, I waken from this dream of folly, and realize that my source clings to Him.