The entire purpose of writing good readable code which is mostly self-explanatory and were it isn't it's properly commented to explain what's going on, is so that it it's not a necessary for the person who picks it up later to be somebody who does remember what that code does and how it does it.

Whilst this is mainly important to allow other people to work in that code, as a side effect the actual person who wrote the code if they follow those coding principles needs not remember what it does and how it does it.

One of the upsides of being a senior dev is having figured this kind of thing out from experience, which offsets the downside that since you're older and have done a ton of things, it's less likely that you will properly remember the details of a specific code base after some months of not looking at it.