I have this problem. Things that I find helpful fall into three categories:

1) Make sure I'm taking care of my body because my brain is part of my body.

2) Make sure I have a super-clear idea of what the task is.

3) Do things to block distractions.

For the first:

- Keep to a regular sleep schedule. Spend $10 on a sleeping mask and buy an alarm clock and white noise machine.

- Regularly eat a balanced diet. If you're poor or super-busy, get a blender bottle, chocolate powder, and Soylent subscription. You can make a meal in 30s and $2 with that. Otherwise, get a slow cooker with a timer and the app Paprika for iOS/Android.

- Regularly do at least 30 minutes of intense excercise. This will improve your sleep and is also great to do in the moment when you feel jittery. Running is good.

For the second:

- Get a notebook and step away from a screen write down what you think you need to do in order to complete the task. Break it down into a super-granular level.

- Make a list of all of questions you need answers to in order to do the task. Often, procrastination results from not actually being able to complete something, but having consciously realized it.

- Send emails with all those questions at once so you give people time to respond.

For the third:

- Download an app like https://getcoldturkey.com/ (for windows) or https://selfcontrolapp.com/ (for OSX) (for linux, this might work http://svn.jklmnop.net/projects/SelfControl.html, but if it doesn't, it is cheaper for you to buy an OSX machine). It lets you block a list of urls for a specified period of time.

- Put your phone in another room.

- Go to https://appear.in/kbody and turn on screensharing. open as many tabs on that url as you have monitors. Then, pay a friend to periodically check up on you and, if they see you distracted, to charge you even more money.