Lindsay Lohan's closest friends have heard all the excuses before -- but several of them now tell TMZ ... this time Lindsay seems to truly understand ... she has a problem.
Lindsay's close pals say she is "beating herself up over this" -- this being two failed drug tests, including one for cocaine. We're told Lindsay "feels like she just ruined all these really great opportunities that were coming her way."
Lindsay's Twitter apology -- where she said, among other things, "I'm prepared to face the consequences" -- "shocked" one friend who couldn't believe Lindsay actually accepted responsibility and didn't make excuses. Of course, the open question -- was that really Lindsay talking or a smart lawyer.
And the other question -- Can Lindsay sway a judge like her close pals?