Masters teach simple & powerful truths. Here are the ones I've come across along with my understanding of their teachings:
Byron Katie - your thoughts cause suffering. Don't believe them! They aren't true.
Eckhart Tolle - Now is all there is. Be aware of it.
Alan Watts - This is it! This is reality.
Jim Rohn - work harder on yourself that on your job
Louise Hay - you can heal yourself by loving yourself