Glen Murray, Shane Duffy and Pascal Gross did the damage for Brighton in the first half, with Romelu Lukaku scoring the Red Devils' only goal before the break.
Pogba added some respectability to the scoreline in injury time from the penalty spot, but he was not happy with the performance.
"We lost, we did not deserve to win," he told Sky Sports .
"The attitude we had was not like we wanted to beat them, they had more hunger than us.
"I put myself first, my attitude wasn’t right enough, we keep trying and pushing, and it is going to be a big lesson for us."
When asked about a disastrous first-half display, Pogba refused to state whether manager Jose Mourinho was at fault.
"The first half, I think you should ask him. I don’t want to talk for other people, I think you should ask him," he added.
United lie in 10th place after the first two rounds of Premier League action, having accrued three points so far.