I think the transition of dropping away from religion has shocked you a little, in that you should look at the things in life that you actually find meaningful to you by yourself, since in the past religion has just told you what is for you. I can't give you an answer because it will be personal to you.
When I was Catholic, I believed that part of the meaningfulness/guidance that the religion at it's depth taught was to live to have a heart for the world around us, externally making an effect and believing that your actions are heard, however small. Even though I'm agnostic now (permanently or not I don't know), I do believe there is some truth to this, so a little of what you found meaningful in the Church could be meaningful to your atheist life.
But, like I said it will be personal to you what you find meaningful. So I think make your own efforts to find what is meaningful to you and find what small moments in life shine, and that would become your guidance
Take care