Camus wants to affirm life – wants to say “Yes” to life.
Have you ever said “Yes” to life? Think back. Was there ever a time when you actually said “Yes” to life?
It is easy to gloss over the affirmative moment and fail to see that every “Yes” presupposes a “No”. As the Kantians would put it: a No is a condition for the possibility of a Yes. No one says “Yes” to life if they weren’t previously feeling negative and doubtful about what on earth they are doing. People who genuinely love life are too busy having a good time to ever stop and say to themselves: “Yes, after all is said and done, life is good.”
Conclusion: If you want to say “Yes”, you’re too late. The “No” beat you to it.