Failed workout

I got to the gym today and just didn't feel right.  I was slow getting set up and then when I went to get into position for a deadlift, I felt something in my knee.  This was something new and not good.  Not pain, but not good.  That combined with annoying stuff on the TV that I couldn't turn off or change the channel on led me to just leave after only about 10-15 minutes.  I'll try again another day.  This is the first time I've ever left a workout after getting to the gym, so I'm not going to beat myself up over it.  Better to leave and not injure myself.