The general knowledge of who an instrumentalist is that: they are people who play a musical instrument ,be it a drum set,a guitar,a piano and the rest, well I would not agree with that kind of definition because being an instrumentalist Is not just by name or title,to be a good instrumentalist there are lots of other things you should know like:
You must love music in general ,not just loving a particular instrument ,you should love every form of music like a boss of mine 
You also need to have the PASSION for it ,before I go on with this I would just give a brief definition of what Passion means ,which is having an intense desire or enthusiasm for something or someone ,you can have Passion for a lot of things but as a musician your passion should be in music ,Now relate that with playing a musical instrument ,what it does is that it brings out the very best of you regardless of how talented or skillful you are.
Don't forget to cultivate the habit of smiling when playing an instrument, especially band members .when you smile you're passing off a positive vibe to your Audience/listeners ,it might seem absurd but it's not ,if you keep a straight face during a ministration you are likely to get a negative vibe from your listeners,so learn to smile 😊
In addition to that you need to be disciplined ,a good number of instrumentalist are faulty in this aspect ,there's even a saying that instrumentalist doesnt listen or participate on any other thing in a programme apart from playing the instrument they are there for,which is totally wrong.most of us barely give offerings in a gathering 😄 neither do we listen to any other aspect of the program as long as it's not playing of instruments which is totally wrong .so we need to be disciplined
Lastly keep striving to be the best,don't relax on what you've known ,let that hunger to know more be your goal,learn to be humble don't see yourself as the best even if you are ,let people be the one to say how good you are,always listen to correction, irrespective of whoever gives it
~~I'm also an instrumentalist (I play the drum set) and these tips has been helpful alot to me personally.
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Thanks for reading 😊
Remain blessed