You literally have all day to make a move in Online chess and also have access to opening explorer and the analyse feature should you choose to use it. In your case in Online games while you are rated 1900 plus you have never beaten a 1900+. try only playing the rating you are trying to beat and you might find that won't lose them all ;)
In live play you have to have a more spot on understanding of the openings as you can't delay moving til you have things figured out. ;)
The biggest difference for me is I play live chess worse here then I play OTB in person.
I would like to know why there is so much difference between the live level and the online level ... Even if I am 1900 online, I am not able to beat 1500+ even in 15+10s time period. Anybody has the same feeling ?