Know that frustration while writing is normal.
Words don’t always come out in the way you hope they do, and sometimes you just don’t know what to say. Acknowledging that you’re frustrated may be enough to reorient yourself in order to try again.
Go back or skip ahead to work on a different section.
Sometimes all frustration needs is time. Try working on something else in the meantime.
Re-read your sources.
Going back through your data, evidence, or primary texts may encourage you or remind you of something to say that you’ve forgotten about.
Take a step back.
If you’re too frustrated to continue, do something else entirely and try again later.