Can you catch anything from yourself? If you are a carrier of something and infect others could you also potentially infect yourself?

Here's why I asked. An Answermug friend (Canadian but I am not naming names) said the trump could possibly get mononucleosis by kissing himself on a mirror. Mono is called "the kissing" disease so I wondered is that possible? To infect yourself with a disease?

Any of you ever had MONO? What was it like and how long did it take you to recover from it?