Ok not that Calm & Relaxed...

Supine poses may be used to start and finish a yoga session.  

Within Iyengar or Restorative Yoga,  asana's such as Vipariti Karani, Supta Badha Konasana, Setu Bandha on the block & Savasana (just to name a few) are often performed by collapsing into the props.  This lack of dynamics lets the body & mind hang about under the disguise of being part of the yoga practice.

What I would like to promote is your part in developing an "internal life" that activates the use of your breath to maintain your asana's form in keeping the mind awake to the tidal effect of each inhalation and exhalation.

This is easier said than done yet vital to your development into Pranayama.  

Savasana being the most difficult to conquer as the body wants to collapse and the mind wants to wander off the mat and into your daily schedule.

My tip - try to see if you can keep your pose actively engaged with as little energy as possible and pretend that you are trying to remove the props you are working on.

Good Luck

NamasTe