I regularly find myself saying, "It's not worth it" in my yoga classes. Your knee is bothering you when going for Bow Pose? It's not worth it to push through the pain and try to make the posture happen. Feeling frustrated that you can't nail your Handstand? The anger and irritation just isn't worth it. It is just a yoga posture after all.
I had a regular student come to me about some shoulder pain she was experiencing a while back. I told her I'd keep an eye on her in class and see if I noticed anything that I could address. During practice I noticed she was consistently dipping her shoulders below her elbows in Chaturanga. On most occasions she was even dropping her chest and face down while using momentum to swing her legs up into a Chin Stand variation. After class I asked her about her decision to take the Chaturanga variation. She said it was something she was really working on and was hoping to be more consistent with the transition. I expressed my concerned about her decision to take such a risky variation when she's been dealing with a shoulder injury. I did, however, take a step back and remembered that I too have pushed through injuries and physical limitations in hopes of achieving a specific yoga posture.
At the end of the day it's just a yoga posture. I never mean to undermine the power of the asana practice, but hurting your body for or beating yourself up over a yoga posture just isn't worth it. Your ability or inability to perfect a posture says nothing about who you are as a human being. Your ability to deal with an injury or limitation in a mindful, safe manner is more valuable than the shape itself.
And remember, when taking a sweet yoga picture for Instagram be warm and prepared to execute the posture. No one likes a hamstring injury because you really needed to show off your best variation of Sundial Pose without proper preparation. Not like I know from experience or anything.