We know that making fun of others should not be done. But how about making fun of myself or let's say roasting myself? Is it haram is Islam?
Yes, it is just as discouraged. Your brain and body work as a unit. One affects other. When you speak something negative, it affects your brain in an unwanted way. Just as an edible can either be good or bad for your stomach, your thoughts and words can be good or bad for your brain. Ultimately affecting your brain and body respectively. Wrong things are not to be spoken or thought about or even remembered.