Merecer - to deserve (use it with actions) For example: No mereces que te hagan esto - You don't deserve they do it to you. Merecerse - to deserve (use it with nouns) Yo no me lo merezco esto. - I don't deserve it. Me merezco una persona honesta y buena que me vaya a querer mucho porque soy una persona muy romántica y buena. - I deserve an honest and a good person who is going to love me so much because I am a romantic and a good person. I hope this helps. If you have any futher questions, please, don't hesitate to ask me. If you need Spanish classes, you can book them right here: http://www.italki.com/teacher/1448117 Have a nice day.

There is not difference, it's just that "Merecer" is a reflexive verb. "Yo me merezco un descanso." Translates directly to the English: "I deserve myself a break." You can also say it this way, but it sounds a little more formal and it's uncommon: "Yo merezco un descanso" (notice the lack of 'me') Both mean the exact same thing though.