I've been through something similar several times. One friend was killed in a car crash, another was left with severe, life changing brain injuries after he crashed, and several friends have died from cancer in the last few years. I'd give my life to bring any of them back as they were all good, kind people who didn't deserve to die so young. But one mutual friend of someone who died from cancer tried to use that a way to stop me from feeling suicidal and I realised that telling someone to "beat" their poor mental health because someone else wanted to live is like telling someone to beat cancer! It simply doesn't work like that. So do not beat yourself up for how you feel. If you need to, do something positive that will actually help others, such as donations to hospice care or research charities or whatever, but do not hold yourself responsible for anyone else's health. That's completely out of your control. Xx