As I stretch, I try to talk to my body instead of seeing it as something hard to get through. It's easy to go too far when you stretch, so I've learnt to pay close attention to what my body is telling me. For me, it's important to know the difference between a little good discomfort and real pain. When I feel a light pull or tightness in a muscle, I know I'm doing something good. But I know it's time to ease off right away if the feeling gets sharp, burning, or like it's in my joints instead of my muscles.
How I breathe is something I think about a lot. Most of the time, I know I've gone too far when I hold my breath or have trouble breathing evenly. In the same way, if my shoulders are tensing up or my back is rising just to stay in a position, I know I'm trying to make up for something and need to change it.
While I hold a stretch, my muscles shake sometimes. It might be okay to shake a little, especially if I'm just getting tired, but I take a step back if it gets too strong or painful. I also pay attention to how I feel after I stretch. Ideally, I should feel open or at ease. I know I probably pushed things too far if I feel sore or achy later on.
Also, every day feels different. My body is less stiff and more flexible some days and more stiff and sensitive other days. I've learnt not to push it to do what I did yesterday; flexibility isn't a set number, and the body works best when you're patient.