Flycut (Clipboard manager‪)‬ 4+

After having lost so many things I was copying & pasting, I used Stickies for a long, long time as a 'temporary' place to store temporary snippets. But... sometimes, I remembered to copy, but not to paste... also, it was a bother to have to do two copy & pastes all the time... and, last but not least, I had a glitch on my Mac and lost *all* my Stickies, so... it was time to find for a replacement!
Fortunately, I saw a site for software developers which listed Flycut as an 'essential' tool to install... and I tried it out, soon to become completely hooked — honestly, I use it so much every day, that I can't even remember how my life was before Flycut! It's such a fundamental tool that Apple should buy General Arcade and make Flycut a permanent feature...
I can't recommend it more. Even if you're not really looking for such a tool, give it a try — after a while, you won't want to go back to have just ONE line of copy & paste...
I'd give it 6 stars if I could... there is just one thing that I haven't managed to put on Flycut: attachments (i.e. images, documents, PDFs, etc.) Maybe there's a way, I just haven't found out how...

After trying and being unhappy with a few paid apps, I found Flycut to work beautifully for me.
It took me a while to find the help documentation, but it is on GitHub.