I think we all hit a wall from time to time. The important thing is to assess how much damage has occurred when that happens, and to make plans to avoid it again, if possible. Since I have no concept of your financial situation, I cannot blankly tell you to take a break from work altogether, but it does sound to me like you could use a well deserved break from the fundraising challenges you face at present. Fundraising is a brutal challenge at best...but it sounds as if you are running a race without heart...when you hit the finish line, there is no joy for having gone the distance.
If you re-read your post, the answer seems somewhat clear, at least from the outside looking in. We can't always be happy with our work, at times even disliking it, but there should be some modicum of joy for the investment of hours you spend. Fundraising is above all driven by a passion for a cause, and frankly, quoting your remarks "I have absolutely no motivation and cringe at the thought of writing another solicitation letter/grant/etc." certainly can't be fair to those who put their confidence in you when you were hired for the task.
IN all your years of work, what did you REALLY enjoy? Pursue that! Sometimes it pays less than the upgraded positions and responsibilities, but pays off generously in other less tangible areas like job satisfaction, peace of mind, enthusiasm and self-respect.
