macOS uses otherwise idle memory for file cache and performance. High used-memory percentage alone is not evidence that the Mac needs optimization.
Look for symptoms
Sustained memory pressure, heavy swap, repeated beachballs, application termination, and poor responsiveness are more useful signals.
Identify the source
Close documents and apps you no longer need. Use Activity Monitor to find a process that grows continuously or consumes unusual memory under a known workload.
Use a supported memory action
Save work first. The action can release eligible caches or encourage reclaiming memory, but macOS and active apps may use it again immediately.
When it does not help
If pressure returns, reduce the workload, update or restart the responsible app, check plug-ins, and restart the Mac when appropriate.
Memory optimization does not increase physical RAM or repair a memory leak. Do not run it repeatedly merely to maintain a large “free” number.