Don't beat yourself up, this happens to everyone. I send updates on the first of every month, good or bad, but only because I was very lucky to have a therapist who told me to man up and keep sending them back when everything was going wrong and I wanted to crawl into a hole and die. Otherwise, I absolutely would have done exactly the same thing.
You can totally salvage this. Honesty is always the best policy with investors, even though it means having a thick skin when some of them push back/complain. Send one for January 2017 on Thursday, doesn't have to be more than 2-3 paragraphs, bullet points are fine. Something like:
Investor Update - January 2017
Dear investors,
First, please accept my sincere apologies for the long silence. It's been a challenging year for , and I let these slide far too long. I want you to know I've been spending every waking moment this past year working on 's success, and if you're willing, I'm ready to resume these regular updates. This will be the first of monthly emails.
Next, an overview of 's progress over the past year. It's been a rollercoaster of a ride, with the team gaining a great deal of first-hand experience with [slower than expected sales cycles, product readiness issues, hiring mistakes, team alignment, etc]. We have learned a lot.
We've also made great strides this past year. We [launched something, increased usage of something, got someone to pay us for something, were featured in the press, made some smart hires, did our first trade show, figured out where we're going & how we'll get there, etc]. The team and I are just as passionate about this company as we were when we started (hah), and we're excited to be applying our hard-won knowledge with our current/upcoming [sales prospects, new users, product launch, whatever].
The journey is long, but we are committed to this company's success, and as always, grateful for your support.
Until next month,
Joe Anonymous