Being a biology student I can explain it slightly... Well our DNA carries our genetic material and is transferred to every generations linked to us and that's why it also proves that we've evolved from gibbons and chimpanzees. So now the question comes that how our DNA is influenced by our thoughts. Think of it like... The food we eat supplies nutrients to our body, our daily activities affects our mood and when it comes at genetic level? Our every cell contains DNA except RBC as they lack nucleus, so our brain cells also contain DNA and whatever we think is transferred to our whole body to react like wise creating memories too and it's all because of our DNA. There are many codons in our DNA that forms what we are whether eye colour, hairs, us being introvert or extrovert or more like our dad or mom. And all our cell activities are controlled by enzymes and hormones that helps cell to go through central dogma and imagine you having bad mood and thoughts? That means stress hormones will be released and will effect the efficiency of our DNA replication and quality. And that's why moms are suggested to stay happy and think positive because that will transfer good positive genes in baby. I know it's complex but I couldn't explain it in simple language as I'm studying biotechnology 🥲😅