I’ve been taught this trick for giving feedback by a couple of people recently, and I’ve been finding it really helpful:

Using “and” instead of “but” can make it much easier to give useable feedback. It also sometimes works in conflict situations:

Eg:

• “I really liked your message, but I thought it was too long to follow.“
• “I really liked your message, and I thought it would have been easier to follow if it was shorter”.

or:

• “I’m sorry that I yelled, but what I was saying was important. Your dog has to stay out of my yard. He’s been digging up my flowers.”
• “I’m sorry that I yelled, and what I was saying was important. Your dog has to stay out of my yard. He’s been digging up my flowers”.

If you say but, it’s often heard as “I know I’m supposed to say something nice, but I don’t really want to.” If you say and, it’s more often heard as “I believe both of these things.“

It’s worth considering erring on the side of saying and rather than but when you sincerely believe both things. It often makes a big difference, both in how you think about what you’re saying, and in how it’s perceived by other people.