"This moment in time, on this tour, you know, I'm discovering a lot of new things. And to be 45 and doing that, it's a mixture of pleasure and pain, I can assure you"

Eric Clapton is expressing his feelings about being 45 and still visiting. He is discovering a great deal of brand-new things, which is a mix of enjoyment and discomfort. He is likely referring to the physical and psychological toll of touring, in addition to the delight of discovering brand-new things. He is likely referring to the physical pressure of carrying out night after night, as well as the emotional strain of being away from home and family. He is also likely referring to the pleasure of discovering new places, people, and experiences. He is likely describing the pleasure of discovering brand-new things and the pain of having to leave them behind. Eric Clapton is expressing his gratitude for the opportunity to still have the ability to explore and find new things at 45. He is likely expressing his appreciation for the opportunity to still be able to experience the pleasures and discomforts of touring.