Nick Stahl -- I'm Finally Turning My Life Around

"Terminator 3" star Nick Stahl -- who's struggled with drugs, alcohol and other personal issues -- says he's finally focused on turning his life around ... telling TMZ, "Everything's getting good."

The 33-year-old actor was leaving the DMV in L.A. yesterday -- after PASSING a driving test -- when we asked him if he's making any progress in the battle with his personal demons.

FYI -- Stahl appeared in tons of big movies like "Sin City," "Bully" and "The Man Without a Face" ... only to watch his star fade after several arrests and mysterious disappearances over the past year.

But Nick says he's back on the rise ... telling us, "Everything's getting good. Everything's turning around ... in a really good way."