Mara is the enemy in our mind, it is the ignorant part of the mind. The Buddha also used the same term. He talked about it, he described it as the ignorant part of our mind that we can identify, and named it Mara. Me on the wisdom side, I have to fight my ignorance side, Mara is my ignorance side.
Why is Mara so hard to defeat? You might as well ask why is the sun shining. Mara has been there, forever and ever and ever, it has been with us; because even the Buddha didn't know what the beginning was, so he would say it was since forever. Mara has always been there, and basically has always been in control; our desires, our aversions, our cravings, our fears, it is all part of Mara. So because it is so conditioned, it has been there not just in this life, the Buddha would say it has been there for thousands and thousands of lives, because Mara has always been in control.
Mara is very, very strong. Mara has all the right conditions. Mara has all the right equipment as well. Mara has every tactic, every successful tactic to make you suffer. Mara is with you as you walk into the hall, Mara is with you when you walk out. Mara is with you when you go to the toilet, Mara is with you when you eat. You take a box, you open it up, Mara jumps out! Mara is just always there and ready. Mara can be a handsome man, and Mara can be the most beautiful gorgeous women, and Mara can be nice and soft, and Mara can be a vicious enemy and a tiger and a terrible demon, Mara can do it all. That is why Mara is so hard to defeat.
Now, how to recognize Mara? Every time you have mental Dukkha, Mara is in control. It is that simple. Every single time you have mental Dukkha Mara is in control. Now, Mara can also be in control in tricky ways. Say you are doing your walking meditation, and you are doing well, you are actually there for a little while, you are really with your foot steps, walking along, getting to the end, and, "Wow, that was good, I can have a break now!" That is Mara being very, very tricky! It says, "Yes, you are doing really good! Now let's go and have a break." You have to recognize Mara is not just Dukkha, mental Dukkha, Mara is a little trickster that is going to take you away from the Dhamma.
The biggest fear that Mara has is that we are purifying our mind and heart. We are destroying Mara. Mara is going to be totally destroyed if we get enlightened. Isn't that fearful for Mara? The ignorance part of our mind is going to be destroyed. It is wonderful for us, as to our wisdom side, but for Mara it is fearful, it is scary and Mara does not want that. Mara does not want you to come and do this retreat. How many of you before you signed up for the retreat went, "Well, ahm, yes, I should go. But, well, maybe I should do..." And how often has it stopped you going to do other retreats? How often does it stop you sitting down on a pillow at night? - I have done enough today, I can quit... Mara is all this. So it is not just the mental Dukkha that you want to recognize, but you also want to recognize every time that you don't want to do the practice, every time that you are kind of falling back to complacency and laziness, as I talked about before. This is all Mara. It may not be a stressful Dukkha, but it is going to try to stop you from growing and learning. So watch out for those two basic forms of Mara.