Radical acceptance of suffering is a key to living life well. I've read that in a ton of places, and I know that's a central tenet of both Buddhism and Christianity, but I thought "life is suffering" meant "numb yourself" or "don't fight for joy."
Life is not all suffering - there is a lot of good, and there are even moments of beauty, connection, and light in the midst of the darkest struggles. But feeling the yuck emotions like disappointment, sadness, anger, grief - that's the part everybody naturally runs from, and this is actually what gets in the way of us loving others and ourselves well in the long run. (Not that we aren't going to struggle with this until we die; we all feel "let this cup pass from me" and I don't know if that ever becomes easy.)
To be a good parent, you have to be willing to feel your child's pain, have to let them make mistakes, have to set them free. That's radical acceptance of suffering. You have to cry when they are bullied as young kids. You feel all the emotions of being dumped alongside them when they are hurt by their first girlfriend or boyfriend. You have to watch and manage your protectiveness as, later in life, they marry a flawed human who is bound to hurt them many times over the course of sixty years together.
To be a good spouse, you have to suffer with your partner, mirror their emotions even when they affect you in ways that don't feel "up." "Mourn with those who mourn" is getting at this. The symbol of the cross is getting at this.
Heck, to be a good grown-up child is to let your parents suffer for and with you! I find I hide my struggles and emotions so as to not cause the ones I love more pain, but I have to be willing to suffer from their suffering about my suffering... :-) We are so connected; we are all one, and the pain always bounces.
"Be it unto me." I'd get a tattoo of that, if I were to get one of anything.