One needn’t max out one’s voice in every single practice session. Some days it is good for the voice and the soul to sing lightly and easily. There is a term in opera called “marking”, which means singing during a rehearsal in a way that is much lighter than in a performance. For lower voices, this may mean singing the high notes in falsetto. For all voices, it might mean taking some parts down an octave. It’s a way to save wear and tear when rehearsals are long, or if the singer is recovering from a cold or other throat issue.
For singers of any style, there are days when you might not have a lot of energy but need or want to practice. Maybe you have to learn some new material for upcoming performances. You can practice a lot of the elements of the music while singing lightly, such as intervals, rhythm, lyrics, and timing. It’s OK to learn your music without a huge effort from the body! Give yourself a break from giving 100% during practice sessions.
Sometimes I just want to end a long, exhausting day with some singing to soothe myself. Letting go of making “big” sounds and just enjoying singing a simple beautiful tune easily and sweetly can send me to bed a happy camper.