Bad High Memory Usage vs. Good High Memory Usage

First of all, high memory usage isn’t always a good thing. If your computer seems very slow, then high random access memory (RAM) usage is not a good thing. If your RAM is full, your computer is slow, and its hard drive light is constantly blinking, your computer is swapping to disk. This is a sign that your computer is using your hard disk, which is much slower to access, as an “overflow” for your memory.
If this is occurring, it’s a clear side that your computer needs more RAM – or that you need to use less memory-hungry programs. This is definitely a bad thing.
However, there’s a clear difference between this case, where your computer isn’t performing well, and the more common case where your computer seems to be performing just fine, but there’s an alarming amount of RAM being used with few programs open.