Emily, you are on a right way.
1. The first thing is awareness. Now you know what to pay the most attention to – hamstrings that prevent you from feeling comfortable in other postures.
2. Plan of Actions. As for that there are two ways which complement each other. Yoga is teaching you that mind body connection. You can work on your body to change your mind and backward – pay attention to your mind to help your body to release tension.
Body to Mind approach. I’d highly recommend Yin yoga. Yin yoga focuses on the connective tissue (fascia) that is surrounding every organ and muscle in your body. So if fascia is tight, muscles are not able to move freely and glide. Then the whole area, the whole group of muscles ( and you have four hamstring muscles) gets tight. Yin yoga stretches are held for about 5 minutes with the use of body weight and gravity and props.
Also don’t forget your lower back stretches. Tight, weak or overworked muscles of the lower back can put pressure on sciatic nerve. As a result – your hamstring will tend to tighten too.
Mind to Body approach. Tension in your body is caused by the mental tension. If your mind is relaxed, your body stay relaxed. In body phycology is it believed that hamstrings is the area where all of our worries are “stored”. Hamstrings are connected with the base chakra Muladhara, which carries energy of our basic survival needs for food, protection, shelter, etc. So if there is some tension about it in your mind. For example you often might have thoughts: “I’m not strong enough”. “I’m not supported enough”, “I don;t have enough”, I don’t feel safe, protected” and so forth. That might lead to tension around that chakra and muscles. Tension in that area also restricts blood flow to the pelvis organs that might lead to some health problems.
So RELAX your mind, let go of worries, and you will see how everything is beautifully unfolding. Simple meditation will does miracles to your hamstring, as well as any other muscle tension.
3. Discipline! Now stay with your routine. And good luck!