I have a late 2012 iMac myself, and I understand your issues. Here’s some things you can try:
If you don’t already have your “Activity Monitor” pinned to your home bar, go ahead and pin it. It’s become my best friend over the years. When your Mac boots up, check the monitor and see how much RAM is being consumed by the OS and background tasks. Ideally it should be using roughly 2gb of RAM. If it’s higher than 3gb, I would look into what’s initiating itself on startup.
Secondly, Adobe CC takes a massive amount of RAM just running the Cloud background software. Without even opening any core programs. I’ve discovered that you can kill the 6 or 7 pieces of CC background software, and still be able to use the core design software. You just won’t have access to your art libraries, and the interactive design assistance, which I never use.
Otherwise you may have to limit yourself, to only two programs at once, and Photoshop can’t be one of the two. PS’s RAM consumption is astronomical. I run InD and AI in tandem with no trouble (takes a while for the programs to load initially) and have Safari running in the background. This usually used up between 6-7gbs of my 8gb RAM capacity.
If you like, send a screenshot of your Mac specs, and total RAM usage, and maybe I can offer further advice.