When performing in an ensemble. It is very important that everyone not only is balanced with regards to dynamics, but also with the amount of playing blending with the group. Here is how I grew to understand my relative role as a session musician in various ensembles...
Have you ever looked at a collection of fine paintings and really studied how the artist used a single color? Let's study the possible use of yellow for example. The amount of yellow the artist selected is dependent on the subject of the painting. A desert sunset would use much more yellow than an seascape would.
The same is true of how much and how loudly you play in a particular song. When I am playing in a big band setting, I understand that the focus of the composition is the horns. I treat them as if they were the vocalists and play more aggressively using more keys to thicken the texture and carry the harmony during the solo sections, but barely playing at all (softly and use open chords) during the tutti sections. With a ballad using a vocalist, I play much more supportively as the role of the horns are to quietly support our intimate combo feel.
Smearing lots of your tone color on every song with no concern for balancing the other colors of your ensemble makes for a very boring collection of tone paintings.
By concentrating on the overall quality of the tone colors and textures with respect to the changing nuances of the music, you will be on your way to creating your own masterpieces in no time.