["I wanted to go to a writing conference. It is a huge and allows you to meet so many people. Unfortunately, something else came up and I had to cancel. I felt so bad that I wouldn't be able to go."]
I am so sorry that you couldnt go as I can see this was so important to you.  Why did you have to cancel?  Must have been something important come up!
I was hoping to go to this wonderful writing contest. I signed up and everything. Then circumstances changed and I had to cancel. I felt so bad that I wouldn't be able to go.