Low disk space is a signal, not just a number
Clearing temp files helps once. Structural fixes help when growth is steady. Know which case you are in before resizing. Educational only — extend only when cleanup no longer matches steady growth.
Measure the top consumers
Use Storage settings and folder sizing tools to find large directories. Move user libraries and dev toolchains when possible — it is faster than repeated shrink/extend cycles.
Hibernation and page files
hiberfil.sys can dominate laptops. Understand tradeoffs before disabling hibernation. Page file moves are possible but rarely the first lever.
When extending is correct
If data must stay on C: and contiguous space exists or can be created safely, extending is reasonable. If not, move data or add a volume instead of forcing risky merges.
Keep backups boring
Automate image backups before partition surgery. The goal is a predictable rollback, not optimism.