10 months on the to-do list

I finally emailed a friend back tonight. Writing that email has been on my to-do list since probably January, but I managed to put it off this long because even thinking of what to write brought up intense enough feelings of guilt that I've basically spent all that time trying not to think about it. I still have at least one other letter like that on my to-do list, but I think that one's going to have to wait. Writing the email tonight hasn't actually made me feel any less anxious about it, unfortunately.
The friend I emailed was a fellow Commonwealthlander at Prestigious U. for the first year I was here, then she went home to finish another degree there. In general, I'm incredibly slack about emailing people at home, but with everyone else, I'd at least send profuse apologies every month or two (or more). I felt even more guilty about this friend, let's call her S, because she lives in another city so when I went home I didn't get to see her to make up for the slackness with emailing. She emailed me her phone number so I could have called her, but I hate the phone so much that I couldn't bring myself to do that and my lack of any rational explanation for my behaviour meant I was convinced she thought I didn't like her or was just extremely rude and therefore she wouldn't like me anyway. So, since then every time I've written a to-do list "email S" has been on there, but as soon as I'd write it, I'd rush to think of other things to write down to distract myself from the guilt and every time I looked at the list I'd do the same and this has gone on until now. I finally made myself write something (basically "I suck. I'm sorry") but it still seems like either not enough or too much (does she even care that I haven't written? It seems kind of presumtuous to assume she would, but rude to assume not - this is my constant struggle in dealing with people) so I have no sense of resolution from finally being able to cross that off my list.
In a way, I was also scared of writing because now, if she writes back, I'll have to write another email and this anxiety is just going to recur. It would be much simpler to just be a hermit and never talk to anyone...