Flexibility is a multi-faceted beast, and the reason so many dancers struggle with developing their optimal flexibility is that what is right for one person may be the complete opposite of what is right for another.
Learning how to assess yourself on a daily basis, and make smart decisions about what you need to do to resolve this, is essential for a dancer. If you are doing a generalised stretching sequence that has not been tailored to you, you will often put in a huge amount of effort for very little reward.
The ultimate assessment tool for this is a simple Roll Down, but the magic is in focussing on exactly what you feel, and understadning what this means. A Roll Down can help you understand exactly where you are getting restricted, as it is often not actually in your hamstrings! Tension in the nerves, fascia or muscles in the neck, back, hips, or feet can limit your ability to go into a deep forward bend.