Creativity is a renewable resource, we can use it for a while, and then it has to be replenished.
Just like planting trees will give us more wood and fresh air eventually, there are things we can do to ourselves to improve our creative production over time.
Creativity doesn't come from a certain spot inside your brain, nor is a manifestation uniquely attached to your life-essence. It's something we as humans put the label into —and can have many interpretations— but there's a very constructive interpretation I like, and goes something like this:
Good associative memory that allows bringing different life-stimuli and productively combine them, i.e. match things to produce something different.
A key-word there is "life-stimuli", like the planting trees analogy I gave you earlier, we can plan creative stimulus in our lives by trying new things, trying the same things differently, meeting new people and cultures, listening to new songs, reading new writings, trying new foods, playing new games, o just breaking the routine once in a while with something unexpected.
In the end, there's nothing new to be said or done, everything has already been created, but since nobody knows everything, we call creative/original/geniuses to those who saw something first and presented it to us as new and fresh (no to belittle their work, there's a lot on merit on putting something out that other's haven't or couldn't figure out).
There's a challenge to be faced when trying to come up with something fresh. We're often subjects of a narrow sight caused by our biases and expectations.
We need to learn to observe —no, for real— and to be able to take the good stuff out of anything, not just by looking at different things, but understanding them, and then comparing and analyzing what we know to try and get a glimpse of what we don't know (yet).
A valuable tool when trying to understand something is the Socratic Method, just keep asking questions and branching ideas out until you hit gold.
Talking about branching, whenever you analyze something remember we are subjects of our own biases, no matter how much you planted stimuli in your creative brain, there's always something to learn and worth listening-to from a different point of view.
There's a lot to talk about co-creation, but that's for another day.