A good fiction exercise is to write nonfiction.
Allow me to explain--when you have an idea or a scene in your current story, a really really powerful moment, you want to get the emotions across just right. Right? (Of course right!) However, in the heat of the moment, there might not be very much Heat in the Moment because you are also bogged down by Other Characters and Subplots and The Setting and Creating The Dialogue and other nuisances.
Which is why you should practice with something you already know. Something where all those nuisances are no longer nuisance-y, because you already know them and they already make sense because the actually happened.
I am talking about a memory.
So write out a memory--a sad one, a happy one, an embarrassing one--and see how you structured it, what words and phrases you used, and maybe even steal some of the dialogue and transfer it to your own story. Then you can write the scene with the hard part--the emotion--already rock-solid and the rest of the nuisances will fill in around it.