This hasn't been updated in a while and has its limits (you can't delete things from servers you've left or archived threads), but it works for me. I consistently purge my Discord messages in all channels whenever I feel like it. https://github.com/victornpb/undiscord I just wish it edited them first before deleting them.
In the future, use names that are not in any way related. A random word and some numbers.
Get an email aliasing service like Addy.io or SimpleLogin so you never have to expose your real email to any services.
Use fake information everywhere possible. Websites dont need to know your real name or anything else except for when you need to enter payment info.
Modify/obscure info you post, and even if you change it. If you have a wife, don't refer to her as your wife, call her your partner, spouse, or something else. Or say "my husband" the next time you post. As long as its not in a context/space that could be negatively perceived. I'm sure there's better examples that might not come off as faking an identity. Like saying your hair/car is a different color.
Don't say "I went to X yesterday", as that gives people dates to connect. Give vague time stamps if you need to. "Recently", "a while ago", "last year", etc. Make it hard to narrow down.
Delete dormant accounts that may have your info attached. Change the names and other details first if possible. Way easier if you have a passeord manager to keep track of them all. No reason to keep a retail store account you haven't shopped at in 2 years. Just make a new one later.