Executive dysfunction is a lifelong struggle. You can't completely overcome it, but you can mitigate it to some extent. Some things that help me:

1. If you are feeling anxious or panicky, don't force yourself to work. Take deep breaths, do something to destress, and get back to work when you are feeling more stable.
2. Try the Pomodoro technique - that is, set a timer to focus on work for 25 minutes, then another timer to not work for 5 minutes, or 15 minutes if your stress level is high. Some system like this, to keep you accountable without compounding your stress, can help a lot.
3. Try working at the same time as a friend. It can create different incentives and accountability to work.
4. Do not worry about what will happen if you fail. You will find a way to deal with that when/if the time comes; for now all you can do is try to succeed.