How does Leonard know about his condition?

Question

After the incident, which caused his condition, he cannot remember anything more than a few minutes old, other than the events before that incident. Yet, he remembers his condition?

Answer 1

All the tattoos listed by Mistu4u help Leonard in guiding himself to cope with his conditions.

However even in this condition he never forgets daily chores like driving, eating, shaving etc. He is also able to use English language comfortably. Through his subconscious he knows about his condition too.

Answer 2

Leonard can not remember about his condition anytime. Even sometimes he forgets what he is doing right now. Remember the scenes when he is running because he is being chased or when he drinks the spitted beer. He just suddenly looses any clue why is he doing something in a time. After the accident, he said he can not store recent memories. But he can remember everything before the accident. But he has to be reminded of the incident (He does it by viewing his tattoos, notebook etc). In his tattoos he reminds himself everything. About the condition he reminds himself. Look carefully:

Left Hand (0:06:50) "remember Sammy Jankis"

He remembered about Sammy Jenkins that who had a special condition.

Left Forearm (0:11:30) "THE FACTS" Circling his neck in mirror image: "JOHN G. RAPED AND MURDERED MY WIFE"

He remembers about the accidents.

Right Bicep: "CONSIDER THE SOURCE" and "MEMORY IS TREACHERY"

By remembering Sammy Jenkins, he remembers he has the similar condition.

Upper Abdomen (Upside-down): "condition yourself" Lower Left Ribcage (Upside-down): "DON'T TRUST" and "HIDE YOUR WEAKNESS"

He is now confirm about his weakness.

13-17) Lower Right Ribcage (Upside-down): "buy film" {Tattoo is in script}, "CAMERA DOESN'T LIE", "NOTES CAN BE LOST", "HABIT & ROUTINE", and "LEARN BY REPETITION".

He reminds himself how he can try to remember things.

This is the way he reminds himself about his condition and the other facts he is looking for. Sam Jenkins is a fictional character through which he remembers he has the condition. Sammy is a character from Leonards memory where memory of Leonard and really Sammy has mixed.

The movie seems to suggest that the "Sammy Story" that Leonard tells is a mixture of real Sammy memories from Leonard, recollections of Leonard about things that happened to him as well as Sammy, projections of things that happened to Leonard but did not happen to Sammy and even some confabulation (common among people with memory problems) of things that Leonard makes up to fill in the gaps.