Naptime struggles (why doesn't my baby appreciate sleep like I do?)

Sometimes it's hard not to get angry with my baby, as sweet as he is. Yesterday he went to daycare again for a few hours. And I don't know how they do it, but he only went twice and those two times they managed to just put him down. And he slept. He wriggled a little, but slept. For an hour. Even more.
While I can not complain about the nights, I still struggle to make him sleep during the day. Maybe it's my fault, I've rocked him to sleep right from the start (as in the beginning the poor thing had cramps that were visibly painful and annoying. Warmth and movement made it better.) And now I admit I still do, or end up doing that. Quite often it only takes minutes, as I've learned how to recognize him being tired. I've tried to put him down tired but awake. Thousands of times. On his back he cries and keeps crying OR he gets very much awake again smiling at me trying to sooth him. On his belly does work. Sometimes. Rarely. He moves his little head from side to side as if he cannot decide on what side to sleep on. I know he does that because rubbing his nose into something soft and warm helps him to fall asleep. But way too often, all that shaking gets him frustrated and awake again all over. Sigh.
So when they told me he had slept without a glimpse of a problem both days he went to daycare, next time he had to take a nap I nearly yelled at him because I KNEW he could do it, he just didn't.
Probably when he goes full days, they'll encounter the problem too. And frankly I don't care how they'll handle it. They can let him cry for a while if they want to. I've tried that one too, only to hear volume rising. Maybe I should've sticked to it at that time, but I find it VERY hard to hear my little boy cry. I know it will be necessary some day. He'll try to bribe me with his tears. And I know I won't give in. I have no problem with putting boundaries (I'm a teacher, I do that constantly).
But for now, he can fall asleep in my arms, if he wants to. I'll try to put him away every time first, and it might work occasionally. But I'm secretly counting on daycare to enforce it.

And he'll do just fine.