I had a similiar experience.
I worked for an agency that had an account that relied on me for creative. When I left the agency to work at another agency, I kept in touch with the client; asked them how their kids were, talked about the weather, and if they were happy with the work they were now getting.
Eventually, they came to the new agency I was at because they were happy with my work and not the agency’s work.
So, keep in touch with your past clients. Bump into them when you can. Give them a call and chat. And, sneak into the conversation your doing the same great work you’ve always done, except you’re out on your own now.
Remember, Jay Chiat arranged many ‘coincidental meetings’ with Nissan executives – he knew where they ate, played golf, etc. and would ‘run into them’ to chat. Eventually, it paid off – he got the business.
Go for it!