If you just want everyone on your card to play nicely, that's one thing. If, however, you want truly polished and refined cards on which everyone plays together with perfect manners, then you have to pay really close attention to placement.
Consider the first card, which is, well, not perfect, but definitely not rude either.
The three leaves (from Papertrey's Mighty Oak) are related to each other in a fan shape above the sentiment. BUT they are just a bit too far apart to be playing perfectly nicely and ever so slightly uneven in spacing, too.
Notice how close everything is in the sentiment (which is very well-behaved, by the way). To get along well with that sentiment, the leaves need to be closer together, too.
Closeness will make a nice, tight relationship and unify the design in harmony and goodness.
Compare the BEFORE card to my revised effort, which is much more unified. Notice how the curves of the leaves are a nice contrast to the lines and angles of the sentiment, but their more organized and unified layout feels so much more intentional than the first arrangement.
I'm all about easy.
But then, you already knew that, didn't you?
stamps: Papertrey Might Oak (leaves), Mum's the Word (sentiment)
paper: Papertrey white
accessories: gridded acrylic block