If you are really stuck and can't get a word onto the page at all. Stop trying. Instead think of what is really bugging you. It could be family with too many demands and needs. It could be a job where you feel too much stress all day to even begin to unwind when you are finally home. It could be an event going on in your life, a marriage, a divorce, a death in the family or a friend, all kinds of little events too.
So write out your feelings. Don't even start with a plan. Just start. Put a word on the page, you might even start longhand instead of using the keyboard. Pull the plug on the damn holding in all your feelings and let them bleed out for awhile. The words don't have to make sense, spelling does not have to count. Vent for awhile, give in to being self centred long enough to spill out all the everyday clutter and poison that seems to litter our minds.
You will know when you are done, there just won't be anything else left to write. Take a break then. Get outside, go for a drive, get coffee, whatever gets you away from the place you were as you wrote. Later, when you are back, decide if you want to read anything of what you wrote. You may just keep it for later or destroy it and get rid of all that pent up emotion. Sometimes you can get a lot of clarity from letting yourself vent thoughts and feelings.
Try writing now that you have cleared your slate.