It'll work, but there are things that put more pressure on your computer. For example, larger high res images, extensive layers. Multiple images open at the same time. Basically the more apps running at the same time (lots of Photoshop plugins and Lightroom all open together) typically make your machine feel like its going slower (if you use too much RAM).
A bit of a dodgy analogy:
You can think of RAM like a Worktop - it is a fairly small size compared with all the cupboards, but you can work on things quickly that are in front of you. If you can fit everything you want to work with at the same time on the worktop, then you can access them all quickly and all works well. However when you start trying to put lots of things on the Worktop is gets too full, you then need to take somethings off the Worktop, and put them back in the Cupboard (disk Storage) which takes time. Then if you need them back you need to start putting others back in the cupboard and swapping what is on the worktop.