To remain energetic, centered and focused after finishing your yoga practice, stay in Savasana (Corpse Pose) for at least five minutes at the end of every session, although 10 to 20 minutes would probably be better. If Savasana is skipped, the body does not have the time to assimilate the effects of asana practice. With a few modifications of Savasana, the effects of the pose can even be enhanced.
It's important to allow the body to relax deeply. First, make sure your body is arranged as evenly and comfortably as possible. Once you're comfortable, start at your toes and work your way up your body, consciously releasing each part in turn. Then begin to release your senses: Soften your tongue and let your eyes drop back in your eye sockets. Imagine your nose softening into your face and your inner ears relaxing.
Next, try to release all effort involved in breathing. It's hard to let go psychologically if you're laboring to breathe, even at a very subtle level. Don't suck or pull your breath into your body; instead, simply receive it, allowing it to flow in.
You can also use a blanket or firm pillows to elevate the chest and head in such a way that the chest (and thus your breath) opens even more.