Take one minute before writing to put yourself into the correct state of mind. What mindset do you need to be most effective in the piece you’re creating now? Is this a serious piece? Then, you’ll want to consciously enter a more serious mood. What other states of mind might you enter, depending on what you’re writing?
It all relates to what you’re writing at the moment. And some pieces require different mindsets on the part of the writer throughout the composition.
Bottom line: Choose your mindset deliberately given the needs of each sentence you write.