What to do after ending affair?

I have just ended an affair that was ongoing for a year. I am not in a good place mentally but I feel like telling my partner will only cause heartache. I am on the verge of just saying that I am going through some things mentally and that I need to be apart for a while, while I sort things out. Mentally I have been checked out of the marriage for a while. I think I need to work on myself before I can be good for anyone else. Does this make sense or do I need to tell.