You've run into this work before, right? And for good reason. It's a buzzword nearly without parallel these days. Whether your concern is anxiety, sleeplessness, IBS, work stress, or dozens more, somebody will mention mindfulness as a tool.
Mindfulness- being here, now- is foundational for relationship, sexual or otherwise.
Lori Brotto, Jon Kabat-Zinn and Vipassana-style meditation are all great (and very different) guides to mindfulness practice.
I think of it as the multivitamin of the wellness world. I recommend finding about more about a match for you and your needs!