Going through the hardest time of my life...

Where to begin? I think what I'm going through right is the hardest thing a human can go through which is seeing someone you love terminally ill and not knowing if today will be his last day. There is a lot pain, lots of suffering, lots of anger and constant panic and anxiety attacks. How can someone get through this? It just feels unbearable. If you had gone through this or are going through this, please, write some advise or share some wisdom.