"Mindfulness" is not the only way to meditate.

I highly recommend this poetic translation of the Vijñāna-bhairava-tantra, a text of Kashmiri Shaivism, written circa 7th to 8th centuries CE. 

Framed as a discourse between Shiva in his terrifying form as Bhairava, and his consort Bhairavi, it briefly and poetically presents a few more than 100 meditation methods, which include variants of breath awareness, concentration on chakras, non-dual awareness, visualizations, and meditations that make use of the senses.

These practices are said to lead to the recognition of the "awesome" nature of Reality (vijñāna means "recognition," and "bhairava" means "terrifying," "tremendous," "awesome"). 

Lorin Roche has been teaching meditation for more than 45 years. He makes it clear in his introduction that meditation is a spontaneous and natural human experience, that there are many doorways into meditation, and that it is helpful to follow the meditation techniques that suit oneself.