I'm glad to see that you are feeling better and in a more positive frame of mind. I hope that writing the letter is helpful. I think it's a great idea.
My sister had a baby 2 weeks before Marco was born. He is my nephew, and I love him, but sometimes my heart aches a little when I see him. I hold him a lot though and hug him and kiss him. He will always be Marco's cousin, even though Marco is in heaven and he is here on earth. I feel that when he smiles and laughs, Marco smiles
I'm glad you are going to see your friend too. I hope it will be a good trip for you.