1. Participate. Nothing forbids you from sharing joy with others.
2. Create new ones. My family, being mostly atheist with a pagan and a non-practicing christian thrown in, now celebrate the winter solstice in June/July as we all love open fires but an Australian summer is not conducive to sipping port in front of one. Nor indeed, to the overconsumption of rich food.
3. Give yourself little rituals of mindfulness and gratitude. We may not have been uniquely created, but we're still pretty bloody unlikely. Remembering that and being grateful for the luxuries life affords is worthwhile. I do it with my morning coffee.
   Every morning I make an Espresso and contemplate the fact that out there in the cold morning dew there's a soldier lying on his belly shivering....and it's no longer me.

I don't feel a specific obligation to emulate religion. Even in a more general sense, just considering how one finds a sense of community / belonging / refuge, atheism is way too narrow a basis for such common cause. Secular humanism, or various charitable causes, probably work better to build those kinds of things.

On a personal level it can be any sort of shared experience. I am making friends with a neighbor right now whose wife is dying; I have no idea and don't care what his religious [un]beliefs might be unless he ends up being an asshat about them. I have something to offer him -- I've been through the loss of several loved ones and I know how to act around that and just be present for him. If he ends up trusting me enough to ask for perspective or advice I can give it. If he needs practical help, I can do that, too. I've already put him in touch with a local men's group I'm part of.

Religion gins up all this mystery and ritual around what they do so that it appears like only they can provide it. And I'm sure only they can provide it in exactly that way. But anytime humans recognize the humanity of others, we can meet the same basic needs as does religion.

Well here’s the thing we can’t at least not in the same way. Here is what we can do: create strong communities that have seasonal gatherings, though those might exist already (I’m not sure). I still celebrate Christmas as I’ve always loved that time of the year and we’ll it was one of the better holidays. As long as you’ve got a good community to spend time with, why not just participate in those already existing? It works for me, but it may not work for everyone.

I always felt religious holidays were celebrated because I had finally left them....