Your clients need, and deserve, recognition on a regular basis. By neglecting your clients because you are searching for new ones, you run the risk of losing the very ones that are making you successful right now.
You also need to recognize that your current clients not only provide work for you, they quite likely will be providing your next client. Word of mouth travels, and travels fast. If your clients love the work you do, they won't hesitate to pass the word along. Similarly, if you fail them big time, the repercussion are far-reaching. If you make a mistake, fix it fast and make sure your client know it was an aberration. Ignore at your peril!
A number of years ago, I had an experience where, quite frankly, I goofed. I made a mistake in a job that was not life or death but it was embarrassing because I should have caught it. I didn't, but the client did. As soon as I read their email, I got on the telephone and apologized, promising to fix the error immediately. Further, I stated that I was not making excuses, but explained how the error happened. I took complete blame and vowed not to let it happen again. It didn't. I was able to maintain a good relationship with that client because I didn't blame anyone else, and kept my word. Necessary steps to maintain my integrity and that of my company.
Your next client may be just around the corner, or they may be on the telephone right now with one of your clients. This is all the business of running a business. It is the face time, it is the phone calls just to "check in" and make sure everything is running well with your current clients. This is marketing that you can't buy because it is without guile. It is just an honest opinion of you, your company, and your ethics. Keep making sure that you deserve the reputation you have built.