Peace be with you!
I personally think that praying even when you aren’t in the state of grace is good for a few reasons. 1.) While it is true you are not in the state of sanctifying grace, God can and does still give actual grace which can help you to repent and come back to Him so as to be restored to sanctifying grace. I have seen that when you pray anyways, it is likely you will return to Him faster than if you stop praying. 2.) It will help you from getting discouraged. It is really easy to get discouraged quickly when you fall into sin. If you pray and ask God for help, it will keep you from losing trust in His power to purify you and keep you from further sin. Often times, when someone falls, they get tempted further to say “I have already sinned. It doesn’t matter if I do this too/again” or “I might as well do this, I can go to confession Saturday.” These are terrible temptations. When you pray and ask God for help, He can give you the grace to keep from future falls and then restore you to grace when you come to Him in Confession.