Getting payments more manageable

I am one who believes in paying what I owe. I have alot of credit card debt some of which I have the interest rates low and some not. My problem is that I have so many payments that I have been robbing Peter to pay Paul and have been getting deeper in debt. I would appreciate your opinions on sending letters to those creditors where either the interest rates and/or payments are high and requesting them to reduce them so I can manage the payments without robbing Peter. I found a sample letter on this website with a format I could probably use to ask for this. Has anyone every done this with success?