It sounds like you’re chasing something that doesn’t exist. There isn’t really like a point you get to when everything is “optimized” or whatever… That word doesn’t really mean anything. Optimization is a process that you use for really specific situations. It’s not a state you get to.
For example, if I was serving a website and the server was showing high CPU usage and disk activity, I might find what files are being accessed most often and add a caching layer (redis, varnish, memcache, etc). That would optimize for more efficient CPU usage and lower disk activity but it would also increase memory usage. That’s a trade off I would need to consider before implementing that change. If the apps I am running are already consuming a lot of memory, I might run the risk of exhausting all the memory and having processes killed off (aka OOM errors). Maybe I try something else then.
You need to find what’s happening with your system and then figure out what you can do to mitigate the behavior of any poorly performing apps. That all starts with good monitoring but beyond that its impossible to say because it’s extremely dependent on how you have chosen to configure your system and what you are running.
This type of investigation is what gets you to be a real engineer.