For me, I wouldn't even share my struggles with my best friend. It's hard to explain exactly why that is, but I don't think I could do it. Some things it would be easier to tell a random stranger at a bar... maybe because they don't have any expectations of you, and you don't have to worry about a feeling of letting them down, or disappointing them or whatever.
Having to maintain a never-ending facade of success and happiness really is draining.
No doubt.
Learning to be able to confidently say "I'm very concerned our company might die if we don't do X by Y because of Z" was one of the hardest and the most rewarding things I learned how to do.
I found that skillfully expressing my real feelings leads to much better results than not expressing them at all. If you pay careful attention to how politicians speak, they often utter phrases like "I'm very concerned about..." It sounds odd at first, almost fake, but when done genuinely it can be a source of great strength. You don't need to fake things in a time of crisis. You can share your darkest fears with people while maintaining a confident demeanor, and it does wonders for how people perceive you.
Of course this is harder to do than to say. I'm still learning, but a while ago I resolved not to hide my feelings from people anymore.