If by 'comfort and guidance' you mean the same type experienced when you believe in a god/afterlife, in most cases there is very little that can give you the same level of reassurance. However, it is somewhat comforting to know that you don't have to live your life based on the law of a religion but instead follow your own moral code; it is comforting to know that you don't need to spend your life worrying about some eternal punishment that is far more terrible than anything in this life; it is comforting to know that we won't live for all eternity but rather have a limited amount of time on this Earth and that we must not spend too much time worrying about the absence of god but rather try and make the most of our lives and do what we can to help others in need so that they might also make the most of their lives.
I can't speak for all atheists, but for me nothing will ever fill the void of the reassurance I once received from believing in god, and my lack of faith is something that I just had to adjust to. However, life is still just as beautiful; there's music, art, poetry, science, films, friendship, family, love, literature, sport, nature and all the other things that make life amazing. It is easy to simply turn to religion to tell you what the meaning of your life is, however it is more fulfilling to discover your own purpose for yourself.
I'm a former Christian, now an atheist.