It’s one thing when life throws you some punches, it’s another when they’re suddenly directed at someone you love. It definitely causes a feeling of helplessness because you can only do so much. I’m currently in the midst of one of these life changes. I’m adjacent to life doing its twisting thing. No one has died fortunately, but it’s an end of an era that didn’t seem like it could end, and definitely not like it did. It’s strange because I would almost prefer it to be happening to me because then I could actively do something about it. But I’ve learned over these past few months of watching the struggle how to help, even if they’re small.
Find out what they need from you without asking. They have enough on their plate and don’t need constant, “if you need anything from me” sentiments sent their way. That always feels like such a half-hearted way to help without having to do anything. Sleuth out the situation and see what kind of help you can be. A shoulder to cry on? A distraction from what’s going on? A place to crash? Figure it out and then offer them clear, helpful assistance rather than a blanket statement anyone can give them.
Be there. So simple, so important. Even if there isn’t a single thing you can do, just being there for the person is helpful. If they live far away, be more active in their life. Call. Write. Let them know that they aren’t alone beyond sending a text.
Help make a plan. Or be a sounding board for them to bounce ideas off of. Ultimately it’s their decision on how they get over the hurdle, but you can definitely be there to help them map out what to do next. 
Be a distraction if that’s what they need. Take them out, come over for take-out. It goes along with being there, but sometimes they just don’t want to think about the problem right away and you can be the one to keep their mind off of it.
Know that this too shall pass and bad days don’t last forever. 
Things have already looked up in the situation I’m currently in and we’re all getting through the change one day at a time. It’s not what any of us wanted, but we’re making the best of it. And that’s really all you can do in the end anyway.