If he's been doing it a lot longer, he's going to get the better of you. If he's 40lb lighter, he's probably naturally faster. If you are less experienced and heavier, you should feel good if you land a few clean punches.

At this point in my training, I'm overmatched everytime I get into the ring. I'm often in the ring with a guy 20 lbs lighter than me, but with 20 amatuer fights and his father is his trainer. We spar with certain rules and limitation so that I don't get killed, but I'm encouraged to throw hard at the kid, because he is getting ready to compete. Trust me, I might be 190 to his 170, but that weight don't mean crap compared to experience and skill. Nothing lets you know the things you need to work on like getting hit. After the sessions, I talk and think about things did right and wrong, and I feel successful to land a few clean ones on a kid 15 years younger with 10x the experience.