Check your /var/lib/psa/dumps directory for a specific backup of the psa database.
If you have it, you can unzip it, and do this:
mysql -uadmin -p<whateveryourpassword>
At the mysql prompt:
drop psa;
create database psa;
Then quit out of mysql.
Then do:
mysql -uadmin -p<whateveryourpassword> < psa.dump.file.name
That will restore your 7.5.4 database.