When things happen you can either control the outcome or not. If you can, and things go sideways, you simply made the wrong decisions along the way and can learn. If you can’t, find out what small parts you CAN influence and do your best to make things turn out okay. If you are totally powerless, remind yourself that nothing lasts forever and you can wait it out until an opportunity presents itself or the situation changes.
Sometimes you will find yourself in a ruinous situation beyond your control. Lower your standards until you have something you can act on - even if it’s going to sleep to give your mind and body some rest. One step at a time, even if they’re small steps and you’re not quite sure where you’ll end up. Find any positive you can. That said, allow yourself to get angry, sad, or anything else you need to feel to vent the stress - but afterward, find a positive and hold it.
Religious people have a built in community around their place of worship or shared interests. If something bad happens, the good people in that community will do what they can to offer support - this is usually mistaken for “god is great, look how he sent you to help.” That’s just silly (and rather insulting).
Atheists don’t have that default support community, but hopefully we have friends and co-workers, people on our dart league, etc. who would jump at the chance to help out when things go sideways. Be social. Help others. Be part of a community of good people, regardless of their beliefs, and they can help steady you when life gets mean.