If I set up my business correctly then I deliver more value to each of my clients individually than they do to me.
However, collectively, my clients deliver way more to me than I do to any one of them individually.
The key to growing this then is to serve more clients but only in a way that at the very least doesn't detract from the value I bring for each one.
Even better, though, is to leverage the expansion process to bring even more value to each client as a result of my collected experiences.