Hello dear students,
I hope everything is fine!
I recommend that after finishing your written tasks you take a couple of days off (if possible) and then read all again to check spelling, grammar or even content.
So, my advice is before submitting your work, take a careful look at it, show it to someone else, a classmate for example, if you wish to get some feedback, go back to your grammar if you have doubts (we all have and tahnks god we do!), breath deeply and then yes submit it!
In case you feel you still need some grammar practice, consider using these two websites related to two great grammar books
Grammar One (Oxford University Press)
Grammar Two (Oxford university Press)
For each book you have several units, and in each unit your have short grammar, vocabulary and listening tasks. Give them a try before or after submitting your final essays!
And of course, enjoy the process!
Have a great life!