system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does epigenetics work?  How much can 
your actions change the genes you pass on, and in 
what way?

What's it all about? How much can your actions change the genes you pass on, and in what way? Can I use this to influence physical and/or mental capability of my offspring?

EDIT. For clarity.
gpt
Your genes are made of DNA. We think of DNA as a pretty static molecule, that never changes or varies once we've inherited it. As it would turn out, there are lots of chemical processes that can happen to the DNA (such as chemicals sticking to it and whatnot). These can happen at any moment in our lives and might have to do with our lifestyle. For example, having a high blood-sugar all your life might sway theses "DNA tweaks" a certain way. These changes are different for each cell, and can also happen in the copies of DNA that get passed on as we're discovering that it seems that sometimes these "DNA tweaks" can get passed on too! This means that we might be passing on effects of a certain lifestyle genetically to our kids. With their DNA pre-tweaked a certain way. It's hard to know how big the effect will be and in what way because we're still trying to understand the exact nature of these tweaks and there's also the nature vs nurture debate where we wonder if they'll have that much of an effect anyways.