I have my MacBook Pro 13' (mid 2012) for 7 months and I've noticed it's getting slower and I've been getting the rainbow cursor a lot which didn't use to happen until a few weeks ago.
I got quite worried about it so I tried to figure out what I could do to increase its speed again, even if it doesn't bring it back to what it was before.
1. Restart your Mac
Usually it's applications that "leak" memory that will make your Mac feel slow, so a restart is recommended. If you haven't restarted your computer yet, do it and return to this post.
2. Check your startup items
Some applications you install on your Mac will add themselves automatically to the Startup Items, this means these apps will open every time you turn on your computer and will spend some memory with their processes.
Go to Apple Menu > System Preferences > Accounts > Login Items and you'll see a list of items there which start automatically when you turn your computer on, you might want to remove some these items if you find them useless: to this, just highlight the item you want to remove and hit the minus button. Be careful, make sure you know what you remove or you might delete a critical system component which will damage the machine.
3. Clean up in System Preferences
Still on System Preferences, take a look on the section named Other (bottom of the window). If there are items on that section, check if there are any you don't use and delete them: just move them to trash. If this doesn't work, you'll have to remove them from the folder ~/Library/PreferencePanes.
To open this folder, open Finder and press CMD + Shift + G.
4. Clean up the Dashboard
Believe it or not, the items you have on the dashboard spend lots of memory of your Mac. Check those items out and delete the ones you don't use.
5. Empty your Trash
You should regularly empty your Trash bin once the deleted items will take precious space of your Mac's memory which could be used to run processes faster and smoother.
6. Keep your Mac up to date
Updating your Mac is very important to make things run well and keep your computer's problems fixed.
I hope this has helped your Macs to run faster and smoother. If you have any question feel free to ask and leave feedback on the comments below.
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