I usually only keep documents and media. Programs can be redownloaded and reinstalled (and it might be better to reinstall them in case you move to a new OS anyway to ensure compatibility).

For docker specifically, only keep stuff that’s specific for your instance; which you normally setup as an external volume anyway. Docker is designed such that you should be able to nuke the container, and all persistent data is restored via an external volume on the host. If you’re not doing that, you should immediately go and set that up now (to get the data out safely, setup a volume connection such that the container path is new - that way you don’t accidentally destroy what’s there, copy the stuff you need out, then readjust the path so it’s correct)

For those who don’t know: