As Maddie stated.
It's all in your mind, if you naturally think "oh I feel like I get the best work out in the morning", you are mentally prepped to do your best then.
There are some variations of metabolic rate differences depending on whether or not you just woke up, etc, but nothing substantial that would largely improve your performance from my knowledge. Unless you have a specific schedule that may affect your performance, (i.e. you have a physically arduous job and you have to decide whether its best to work out before or after), no biggie.