Not knowing anymore about you than you wrote, my gut is that your problem is one of 2 things:
1) You lack a compelling value proposition for your clients. Something like, I'm really good at X, better than anyone, hire me.
2) You don't follow through with clients, finish the job etc. so you don't get referred business.
I seem to notice that the HN crowd, and even finance crowd completely ignore marketing. This is a huge oversight that is likely to cost you a ton of money.
I'd read this: How to Close Every Sale (Joe Girard)
The guy is a used car salesman that looks ridiculous, but the book is actually good and there are several big lessons to learn in a very small paperback for less than $10.
I applied the concepts to selling $10m+ apartment buildings with 3 to 6 month sales cycles. The big lesson is that you must always assume you will get the sale. If you are doing things like writing emails in a timid way, no one respects it. You must assume your interactions with others will result in results.