I bet you are being too hard on yourself. Try practicing with more softness and forgiveness and with fewer expectations, less demands, and fewer rules. Remember to make use of the structure of the system but also exercise the freedom to interpret the structure widely. It ought not be a secret that you and only you are the main person to please each time you practice. That is why it is a cardinal rule to allow your own sense of enjoyment to play the leading role in guiding and directing your efforts in practice.
Use enjoyment to refine and recalibrate what you think your practice is supposed to be and what it is supposed to do for you. When you step on your mat and confine your senses within your inner borders allow ample space to just be there—without a pressing agenda, without a need to do a set number of postures, without needing to have a specific level of strength or flexibility. Curiously train your mind on your breath, invest in your movements and find an interlude of stillness in each pose. Allow yourself to simply fiddle around, explore, research, tinker, visit and revisit, and just plain old muck around each day---see what kind of beauty can emerge. And don’t doubt it---you can trust that beauty will spontaneously arrive—maybe in tiny bits and pieces, in a few brief moments during Downward Facing Dog or when you discover some tiny new thrill in a jump through.
No matter its duration or what form it takes savor any enjoyment and be receptive to the agreeable moments whenever and wherever you find them. If you are lacking motivation or inspiration one good place to start whether you are a beginner or a veteran is to focus on the basic techniques of Hatha Yoga: Ujjayi breathing, connecting your movements with your breathing, 9 positions of Surya namaskara, Standing postures, seated forward bends and twists, or possibly Inversions. Listen to your breath as a means of tuning in to your inner dialogue. At first many scattered and irregular thoughts will be there. But soon as you regularize your breath and movements--watch how your inner dialogue changes and your focus automatically turns towards enjoying your posture and your breath in this very moment and before you know it you’ve logged in a practice.