Sometime in the past year I read a quote from an oboist for a famous orchestra. (I would credit him if I could remember who said it so let me know if you know who it was.) They said "I play music for the (famous name here) orchestra on the oboe." That simple sentence is quite profound. He didn't say "I play oboe" he said "I play music." Playing the music is key. Not playing notes, not playing the whistle, but playing the music.
Many people start playing music on a penny whistle because it is not very complicated to make notes with. This is a good thing because you can more quickly forget about the mechanics of the notes and get to the music. Once you get to where you are playing the music, you will find that music is what comes out, not just notes. It will come out of your mouth when you hum it, it will come out of your lips when you whistle it, and it will come out of your penny whistle when you play it.
It will take a little time before your body will automatically make the sound you want on any chosen instrument, and until you reach that point you will be aware of the mechanics of playing each note. This is a place we must all pass through, but we don't want to stay there and learn to play each note faster and more precisely. We want to be able to forget all about the act of making the notes and just make the music. Speed and accuracy will take care of themselves since the music will sound better and that will reinforce the learning.
There is no short-cut. You have to train your body. The younger you are when you start, the quicker it will learn, but there's not such thing as too old to learn. Maybe too old to learn quickly, but since learning is fun, it doesn't really matter how fast you learn does it?
Once you can play the music, you will gradually be able to think other thoughts while you play. Most say when they started they were aware of playing the notes, hoping the result sounded like music. It took a lot of concentration. Personally I couldn't even look at anything moving or I'd get thrown off. Then people say they listen to the music they are playing and in effect play along with themselves thinking the music. The next level is being able to think about things other than what you are playing. Things like "What tune should I follow this with?" which isn't real hard to manage when you are ready, but also "How does it go?" which was a little trickier as you are playing one tune while thinking up another.
So focus on the music. If you can't hum or whistle a tune, what makes you think you can play it on an instrument? The music has to be in you before it can come out again. So listen to your chosen music a lot, and make sure it's really in you. Really in you. All the little details that make it sound like what it is. Then it will be a lot easier to share it with others through your playing. Because that's what you are doing. You are not "performing" you are sharing the music that is in you.