When I first went to art classes, keep a sketchbook was one of the instructions. As it was never explained why they'd be useful, the words went through one ear and out the other, never pausing to gain a foothold in my brain!
I had such a rush of ideas I wanted to commit them to the watercolour paper and paint them straight away - which I did. Anyone who was foolhardy enough to say "I like that" would find themselves in possession of a painting - so the idea was lost to me. I gave away lots of my early stuff, just delighted that someone liked it.
Now I realise that I have improved - if I had kept a sketch book I could have gone back and re-used those ideas. I try to draw a sketch a day (sometimes I fail) like the little chicken above. He's there in my sketch book and I can use him as a reference for a whole painting or I can slot him in, in a smaller version , in another painting.
I try to sketch a little thing which interests me, an animal, a door, a window. They aren't full paintings by any means, but they remind me what I found inspirational or enjoyable to look at. I can always use them, even if I give the painting away!
So, if you want to paint, keep a sketch book. Here's what one little sketch of a chicken led to..