My sons are approaching their mid-twenties now, and both have mental illness.
My eldest has a serious psychotic illness and autism. He is a very gentle and vulnerable young man, and the medication has made him gain a lot of weight which really effects his health. I am working with his support team to try to help him make healthier choices, but his eating is emotionally driven. His illness cost him his education. He left school at 14, and was in and out of CAMHS units until he went into residential living at 18
My other son has a serious eating disorder, OCD, GAD and is being assessed for autism/ADHD. He also left school (or was unable to attend school) at 13, and has been seen infrequently by mental health professionals over the past decade. He is extremely avoidant. I work from home, and keep a low arousal environment for him. I hope he will take up online learning. He is very intelligent, but afraid of commitment.
My husband also has a serious mental illness, and is in a care home. How is currently experiencing delusions, but we like to see each other twice a week.
When we all lived together the situation was very difficult, and one of the reasons that I began working from home was so that I could combine work and care.
In answer to the original question, I do not think I coped. I think I broke a hundred times. I broke when the family had to part. I broke when my eldest had to go into care (although he was an adult). I broke when my husband went into care (although we no longer lived together). I broke when I realised that my sons were not going to complete school, go off to college, go to work and so on. Their paths were unknown.
And it is because mental illness is relentless. It can have such an impact on the individuals' lives and the lives of all members of the family, that it is so important to try to preserve our own mental health. I swim and cycle when I can. I read. I have a job that I love, and my greatest aim is that my sons and my husband are safe and happy.