Here is a brief article by Kim Allen that describes feeling-tones (vedana), and why they’re so important in mindfulness practice: The Power of Feeling Tone.
There is a resource page that lists a number of articles, guided meditations, and recorded talks on mindfulness of feeling-tones. You can find that page here: Common Ground Meditation
The Introduction to the contemplation of feelings (i.e., feeling-tones or vedana) at Access to Insight is very good and discusses how to be aware of feeling-tones both in meditation and daily life, and then to be aware of the connection between those feeling tones and our emotional reactions. You can find that Introduction here: Contemplation of Feeling
If you have difficulty judging your thoughts during meditation, and judging your meditation practice, the following article by Diane Winston has some good suggestions for how to bring kindness and compassion to our tendency to judge. You can find her article here: Three Steps Toward Self-Compassion