Setting Array Value

I want to make it so when, tirednessNumber == 1 it will switch to “Element 1” which is picture “bar1”. Thank you in advance.

Read the 1 documentation. There’s a sprite property that you could use:

TirednessUI.sprite = TirednessSprites[tirednessNumber]; 

Just take out all the if statements, and leave one thing in update:
spriteRenderer.sprite = TirednessSprites[tirednessNumber];
This is much simpler and less cluttered.