Atheists lack belief in the supernatural, but what are the ideals of your atheist life? What is the meaning of existence to you?
First of all, atheists do not all lack belief in the supernatural, but I certainly do. Everything that exists is natural, and there is no other "category" of existence. There is no such realm as "outside" of existence. That's not sad and depressing. That's not a problem. All there is is enough for anybody.
"Idealism," philosophically, is the idea that there exists a realm where concepts are realized--they are actual objects. Of course, I do not have this belief. Ideas exist in the brain as combinations of neurons or psychological entities. I'm not sure that the questioner means ideals in this way. Taking this into context of life and meaning, I can only imagine he or she is thinking of beliefs about purpose of life, and perhaps values. That's because existence is not inherently meaningful. It is an absolute and irreducible. It simply is.
What is it that I think that might possibly make me sound less than completely difficult? I don't like to put words in people's mouths. So, here goes. What is the meaning of my life? What are my values and goals? What do I "believe" in? I exist because my parents had sex. The universe did not intend for me to be in it. But because I am here, I want to enjoy a rich variety of experiences, so that I feel that I have used the little time I had alive to the fullest. A part of me wants to tear through the world, and another part of me wants to make sure that I leave as little mess as possible. I'm just glad I'm here, and hope, that in the future, I will be able to teach others how to ask better questions. Oh, and it's not an "atheist life." It's a good life, in a godless world.
But thanks for listening, diary.