Right, hopefully from the previous two parts, you will have been able to determine the type of block or impediment that you have because there are very different solutions.
For example, if you are suffering from true writer's block, there is no point in trying to sit down and write. You need to get away. To do something else. Possibly structurally creative like sewing or cooking. Reading outside the genre you are writing may or may not help. You also need to give yourself time. Time to refill the well. Make a contract with yourself that you will take time and make it specific. Then go back and try. If you are experiencing the same thing, repeat. You will know the difference.
If it is FEAR, taking time out will only exacerbate the problem. So what can you do?
1. Write and write every day. The most successful writers write something every day because the story is fresh in their minds. Set a minimum goal. A paragraph can be enough. A sentence. Four words even. Work regular hours. Set up a schedule. I get up early and work then because my subconscious has been working while I sleep. Some people work better at night. Know your work pattern. Take regular breaks. Reward yourself with breaks.
2. Get away from your computer and all electrical equipment and write long hand. Rediscover the joys of putting ink on paper. Scribble a note on scrap of paper. Then go back to the computer and type up what you have written. In this way you have a definite task. I do this one a lot.
3. Simplify your rituals. Everyone has rituals (see Twyla Tharp's The Creative Habit) but sometimes those rituals become all consuming and do not leave any time to write. Books have been written in noisy offices, with screaming babies, on trains, planes and the kitchen table. You do not need two hours to get a sentence down. You do not need a clean computer screen or all your emails answered. Or your blog updated. Quick and easy is best.
4. Write a simple generic sentence, knowing that it is easier to fix a bad page than a blank one. You do have to remember to go back and revise them. But one sentence means that you have started. And one word follows another. Force yourself to open the file. Learn to work with the entire document rather than dividing it up into individual chapters. For example, use bookmarking. Ctrl end will take you to the end of the work. Insert break will give you a chapter break. that way you are not constantly starting with a new document. But remember to backup.
5. Force yourself to finish. Commit to the end. Write the ending or decide what you are going to give yourself as a treat. Work on one book at a time. Or have definite times to work on each project. For example James Patterson apparently moves around the dining table, with sets of papers. When he is sitting in a specific chair , he is working on a specific book.
6. Have a definite place to work. Make sure all your tools are there and you do not have to search them out. But remember writers have been known to read dictionaries and thesauruses for entertainment or distraction. It is amazing how attractive a dictionary can become at times. If you use the internet as a distraction. Make sure your workplace computer is not connected. Keep your work place simple.
7. Get exercise. Exercise frees the mind. Dickens and Kipling both used to walk miles every day. Walking improves the spirit. Getting outside can make you notice things. Movement. You see things and perhaps even come up with ideas.
8. If you really think your work is POS and hopeless, try this exercise. Bernard Cornwell did it. And it may help with your confidence. Find an author you admire. Take a scene in the middle of the book. An average scene. Type it up in the font you use. Print it out. Read it again. It probably looks different and not necessarily as good as you thought. The printed page looks different to the typed page. And ALL writers write average scenes at some point. Not even Dickens or Shakespeare wrote pure genius. Then go back and look at something you wrote. It worked for him.
9. Read about how other authors work. See what their habits are. What fears they fall prey to. Know you are not alone. I think it is Paris Match that has hundreds of interviews with writers about how they work.
10. Avoid crutches such as alcohol or drugs. Ultimately they sap creativity. Know that the creativity comes from within you, not from anything else. It is the desire to write that shows you have talent. Everything else is learning to control and maximise that talent. But learn to relax.
These are just a few suggestions and hopefully they help.