That Sucks! The words I think but never say when expressing compassion for trials

As a teenager I often used the word "sucks." It was a common slang word to express disgust or discontent of which I felt a lot as a teenager. One day I was talking to my parents in their bedroom and said "sucks." My dad stopped me and said, "Never say that word again." "What word?" I said. I didn't even know what I'd said that he thought was offensive. He explained that "sucks" was a vulgar word and I could use better words to express myself. Since then I've avoided saying it. But recently I've thought it a lot.
While visiting my daughter's Relief Society, a meeting for women, we were discussing trials and one woman raised her hand and said "Sometimes the only appropriate thing to say to someone going through a trial is 'That sucks.'" At first I felt uncomfortable with the words she used, but now I think she's right. Saying it about every little thing that goes wrong like I did when I was a teenager is inappropriate, but when hard trials happen those words express our disappointment and compassion.
From the last month, here are some things that suck:
A friend's twenty-four year-old son has colon cancer.
A friend's father has stage 4 cancer and only a few months to live.
My teenage niece had to stop going to school because she's very sick, is losing weight, and we don't know why.
Our foreign exchange student visited with us from Switzerland and when she flew home, her luggage was lost for about a week.
My friend's car broke down on the way home from her daughter's wedding in California.
I won't say out loud, "That sucks," but I might say, "That's awful" or "That's rough" or "That's hard." A few weeks after our dog died, I saw our veterinarian and he asked how I was doing. I told him that now that the children have started school it's very lonely and quiet in the house without our dog. He said, "That's really hard. Yes, that's hard." It made me feel better.
It's hard to know if you've said the right thing. Many years ago I heard that you should never say, "I understand what you're going through" when people are facing a trial. Most of the time you haven't gone through what they're going through so you can't understand and even if you've gone through something similar, you aren't that person having that exact problem. So to be more compassionate I say, "I've never had that happen. I don't understand what it feels like, but I'm thinking of you and praying for you." Recently my sister-in-law told me that after a trial she had, I wrote her a letter and told her I couldn't understand what she was going through and offered sympathy. She took my words as almost a mocking of her trial and that I was being insensitive by telling her I couldn't understand. Of course that's not what I meant and later after she was not so overcome with grief, she understood.
What is the right thing to say? Two years ago my daughter miscarried twins. Another sister-in-law lovingly contacted my daughter and said, "No one will ever say the right thing to you, because the only right thing is, 'I will fix this.'"
The Savior, Jesus Christ, is the only one who can truly fix our problems. And He most often doesn't do that by taking them away. He offers us solace when we pray, strength when we think we can't go on, service from others, and a softened heart to notice our blessings amidst our trials. The right thing for us to do when others are suffering is to love them, not avoid them, and hope that after their grief has dissipated they will realize that our words were meant with love.