It became a habit of me I want to get rid of. But you should understand this. People always prefer the shortest way to express themselves. Because of that for example maybe a hundred years  later  "u" can take the place of "you" in written language.

 

 

 2mrw???? What on earth are YOU talking about, Marion? I´m a foreigner in English, remember?

 Is the "I " word also an abbreviated form of an old English word?

  

before 900; Middle English ik, ich, i; Old English ic, ih;  cognate with German ich, Old Norse ek, Latin ego, Greek egṓ,  OCS azŭ, Lithuanian aš, Sanskrit ahám

Reduced to i  by 1137 in northern England, it began to be capitalized c.1250 to mark it as a distinct word and avoid misreading in handwritten manuscripts.