Many of us might have switched over to streaming services without so much as a backwards glance, but iTunes still has some advantages going for it -- not least of them smart playlists, and the ability to customise them as you see fit. Using the comment fields and your own choice of hashtags you can create personalised playlists for any kind of mood or occasion.
The hashtags you use for this are completely up to you. Some good ones are #instrumental (when you don't want to be distracted by lyrics), #ohsoquiet (when the rest of the house is in bed) and #roadtrip (for... er... road trips). You can use as many different ones as you like and combine them as required.
Right-click on a song or group of songs and choose Get Info to make changes to the comment field. Anything you enter here can then be looked for in a smart playlist; choose New then New Smart Playlist to set one up (or click the plus icon in the lower left-hand corner of the playlists interface).
For example, create a smart playlist limited to five tracks picked at random where the comment includes "#instrumental". If you add the condition that they haven't been played in the last day, the playlist will repopulate automatically as you go through it. You can combine hashtags too, like #upbeat and #alltimeclassics. It's just another way of being able to sort through your library beyond the fields you're already given.