Is this something about yourself that you need to resolve or do you just need a technique that fixes it so you can work? The other answers tell you how to "fix" it.
If it feels more personal, then I would make it even more personal. Sit down to write on the computer. Write about how that makes you feel. What or who does it make you remember? What exactly seems wrong?
If it works for you, you can even personify the computer (not with all the other things it's good for, but just "who" it is in this situation). Then, you can talk, argue, yell, or plead with it - whatever feels right at the moment.You can even have it answer you, goad you, or comfort you - whatever spontaneously happens. Don't let yourself analyse it until later. Stay in the moment.
If you get into it enough, you may experience emotional release from giving these feelings voice and if the flow is good, your subconscious may even reveal things to you about why you have this issue.
Sometimes just knowing that is enough to dissipate it. Other times, it may lead you to actions which lead toward a resolution. Or, maybe, you will come to feel that it's OK and that you just have to work in a different manner for now.
It doesn't really matter as long as the "answers" come from within you and feel right to you.
Don't expect all of this to happen immediately. Issues such as this are often layered. You might have to (as one possibility) first express anger or frustration to get to sadness to get to some clarity.
You might even end up with some material you can use later in other things you write.