Once I read a book that said if you start your yoga practice after your mid 20's, it's as though someone has given you a folder of all the events in your life and it is up to you whether you want to read it.
I have to agree that when we arrive on our mats there is nowhere to hide. You show up and whatever is revealed is a reflection of your daily life or past experiences. Our job is not to become our biggest critic when some days reveals your distracted mind or maybe your energy level is heavy and lethargic. This becomes an opportunity for Self Study, a situation when you recognize that your not focused and to train your mind to come back to the present. If you are tired, take the rest you need in child's pose to breath and concentrate on each inhale to capture more prana (energy) for when you leave your mat.
Whatever you do off your mat will show up like a mirror when you start practicing. If you played hard in the mountains and went out for a late night, your body and mind will let you know; your balance may be off or the stiffness in your legs is noticeably limiting your flexibility The point is not to be hard on ourselves and to take each drift in thought, ache in the knees as a chance to treat ourselves with care and respect.
Svadyaya ~ Self Study is the 4th of the Niyamas found in Patanjali's Yoga Sutras. This ancient yogic text reveals the 8 limb path: various steps and processes to achieve a state of enlightenment including the bumps we may encounter on the road and how we may overcome them. Through Self Study we learn what some of our habits might be, this can be as simple as always stepping forward with the same foot or purposely leaving out certain postures. We also get to see what serves us well; that smiling really does ease tension and laughing when you lose your balance is ok. The idea behind studying is to create a sense of union with ourselves and those we come into contact with. All we can do is try our best and be willing to accept and look at our whole self with the same attention we give our loved ones.