Put It Into Context
Improvisation is a lot like speech. The words (lines, licks, ideas) are part of the language (Jazz or other genre). The difference between a great orator and and a child is how they construct their sentences. It's not enough to put words in the right order. Your pacing has to be good, use of space to highlight or lead up to great points, and the context has to make sense.
One of the keys to improvising, especially when starting out trying to find your own voice, is to put things into context. That means when you find a good line, whether one you created or one you learned, you have to put it into context.
If we compare this to language it might look something like this:
Let's say our new found line is the phrase: I love to have donuts in the morning.
New improvisers take their new line and put it into a sequence like this:
"I love to drive red cars. I like to hang out with my friends. I love to have donuts in the morning. I like going to the beach."
The ideas are random and don't make sense together. Individually they're fine. Together...not so much.
However, great improvisers will do something more like this:
"After a long night of working at the club and getting 4 hours of sleep; I love to have donuts in the morning. Especially with coffee. You probably know the feeling as well. There is something about a soft sugary pastry with caffeine that gets me going."
Notice how the line fits into the story? It has context. Not only that, but everything after had a continuation to further the idea.
That's what we have to do when we improvise. When we find something we like, we have to put it into context. Practice by playing something slightly before and after the phrase so you can work the idea into a context.