Keep Originals
When possible, keep the fullest version of a file you have. A compressed image posted to a feed is great for sharing on your site or social media, but it should not be the only surviving copy of the work.
Retain scans, high-quality photos, exports, layered PSDs, source files, layout files, PDFs, and other materials that might help you revisit the work later.
Save writing alongside images when you can: image captions, dates, artist statements, or even just memories of making the work. These thoughts often become more valuable context as time passes. It allows us to have insights into who we were and gives us the opportunity to learn from our own personal histories.