By default, LaTeX inserts some space outside the parentheses when using \left(...\right), which often results in awkward spacing, such as when the parentheses contain the argument(s) of a function:

Code: 
\sin\left(\int_0^t f(t)\right)
Output:
$$\sin\left(\int_0^t f(t)\right)$$

The mleftright package allows us remove the extra space between “$\sin$” and “$($” without manually adjusting the spacing. Once mleftright is loaded, you can remove the spacing for specific parentheses by replacing \left with \mleft and \right with \mright. Instead of modifying all of my \left/\right pairs, however, I use the following code to replace the definitions of \left and \right:

%%%% Fix Spacing Around "\left(\right)" %%%
\usepackage{mleftright} 
\mleftright % redefine \left as \mleft and \right as \mright.

Then, the no extra spacing occurs throughout my document:

Code: 
\sin\left(\int_0^t f(t)\right)
Output:
$$\sin\hspace{-3mu}\left(\int_0^t f(t)\right)$$