The defender was part of a Hammers side that saw a half-time lead overturned when old boy Joe Cole equalised, before James Collins put through his own net.
The east London outfit now visit the Hawthorns to take on a West Brom side seeking their first win after a run of three straight defeats.
"Our aim now is to get back on track against West Bromwich Albion," declared O'Brien.
"We want to take the points but it is a hard place to go and they have a good home record.
"Hopefully we can get a result but, as you saw against Liverpool, the top teams can produce little bits of magic and you are suddenly behind.
"I thought we played some decent stuff and created some good chances particularly in the first half down the right with Matt Jarvis. We looked good and that is what is disappointing because Liverpool did not play us off the park."