Scientifically nothing can change your DNA but you can change how it is expressed. The company I work for found ways to express the younger side of DNA using nutrition. However aside from some very nasty chemicals there is nothing that can change DNA.
You shouldn't give up though. There is much we don't understand about the brain and its role with the body. I am 30 (transgendered Male to Female and cant afford or qualify for Sh!t. I try every year) and I constantly get told I look 19, idk if it is good genetics or if the files I have been using since I was 18

helped. Scientists just have no idea what the brain can actually accomplish on its own body. And there are no studies done on it because science doesn't believe that the brain can change the body at all. plus to test such a hypothesis would require someone either 100% believe they can do it or a person who has never been in a science class relating to the human body or DNA. (any preconceptions could screw the results considering the type of test)
Metaphysical is another approach that doesn't have much info because of scientists disapproval. Which scientists kind of put hypnosis in that branch which is good news for us. Hypnosis has its start as that crazy thing that gypsy's use in traveling acts. Since then it has been adopted by therapists and the psychological community which does legitimize the hypnosis community. But still there is not a lot of info about that still because of the uneasy relationship with the scientific community.
And I appreciate your restraint about our current president. I personally didn't like Obama because I have been hurting economically for years, like the rest of my generation. I am not pleased with our current president but there are good and bad things I have seen come from him.