Writer's Block is described as an inability to write, which is not due to lack of skill. According to Wikipedia it is often due to lack of inspiration or lack of confidence, or a feeling that the particular project is too overwhelming.
One of the suggested solutions to Writer's Block is to attend a Writers' Group, where there are other writers who may suffer from the same condition. The group offers support to writers, and also the opportunity to start writing again, by the use of writing games and exercises, as well as the discipline of having to produce something.
Another suggestion is to write about reality. Going to a new place and describing the scenery in as much detail as possible, analysing the character of someone you know, reporting on a conversation you've had, or journaling your feelings are all ways of returning to writing.
Reading is the obvious source of inspiration and learning, and we can gain much from observing someone else's style, but it is important to write with your own "voice," in your own style. People often worry about how to develop their own style, but this is something that should come naturally, in the same way that speech comes to us naturally.
Writers are their own worst critics, and it often seems that the more talented they are, the more harshly they assess their writing. They hesitate to start until they are confident that what they produce is near-perfect, but in reality, the best way to start writing again is just to sit down and write, without worrying about the results.