[Presented at Know Thy Star, Know Thy Planet conference]
Searches for rocky, habitable zone exoplanets have naturally moved to surveying lower-mass stars such as M dwarfs. While geometrically favorable for exoplanet studies, these small stars present serious challenges for habitability characterization and transit detection due to surface magnetic activity, especially from flares. To fully "Know Thy Star" we must therefore understand its magnetic activity. I will review how exoplanet missions such as Kepler have begun a revolution in our understanding of stellar activity, including the first models of flare rate evolution over time. I will also discuss how flares have impacted the search for planets around M dwarfs including Proxima Cen and TRAPPIST-1 in the optical and IR, and the prospects for future work on active stars.