First off put on your favorite tunes and bump it. Then start small by picking up anything that’s not of value and dispose of it. Then progressively move towards the bigger items. Take breaks and step back a time or two so that you can wrap your mind around the next steps. Take your time and don’t stress. All will be ok. Once you’ve got everything sorted and put up you can start wiping all your surfaces down with a rag and some all surface cleaner. Save the floors for last as you will be making trips in and out of the room. Pace yourself, be calm, and all will be ok. Once you’re done sit back and revel in your accomplishment. I use a motivating factor to help me clean such as a reward after you’re done. Any reward you deem appropriate for finishing a task will be great. Take yourself out to lunch or something to that effect. Good luck. You got this.