Despite taking the lead through Tomas Soucek in the 83rd minute, West Ham were undone by late goals from Carlos Baleba and Kaoru Mitoma, who sealed a remarkable turnaround for Brighton in the final five minutes.
The result leaves Potter with only three wins from his 14 matches in charge, and his dissatisfaction was clear during his post-match press conference.
"We did a lot well in the game, but the pain right now is quite difficult to process," Potter said. "The lads are devastated. We're all devastated."
Potter acknowledged that while there were encouraging elements in the performance, West Ham have consistently struggled to maintain their level over 90 minutes.
"We're not able to sustain what is required to win matches in the Premier League at the moment. That's the reality," he added. "We've found ourselves in promising positions in recent games but haven't been able to hold on - each time for different reasons."
When asked to respond to chants from West Ham supporters calling for striker Niclas Fullkrug's introduction during the first half, Potter was succinct: "They're entitled to sing whatever they want. That's it."
He also dismissed speculation that Fullkrug's omission was linked to a controversial post-match interview the forward gave after last weekend's draw with Southampton.
"We make decisions based on what's best for the team in each match," Potter explained. "We need to consider how to support the players in the latter stages of games - whether through substitutions to tighten things up or to change the dynamic. There's always something we can adjust."
Despite identifying many aspects of West Ham's play that were positive, Potter admitted such points felt hollow given the outcome.
"There are a lot of positives, but no one wants to hear them. It doesn't matter," he said. "I'm tired of talking about positives."
With just four matches remaining in the season, the manager emphasized the importance of unity during what is proving to be a challenging period.
"We have to stay together. The next four weeks will be tough, and we must support one another."
When asked about comments from Brighton manager Fabian Hurzeler concerning his team's late-game strategy, Potter offered a measured response.
"Whenever you win, you're seen as a genius with an elaborate game plan," he said. "I can't speak about Brighton - I don't know their plan."
Potter concluded his remarks by expressing the emotional toll the recent string of results has taken.
"Honestly, I don't feel like talking about anything positive right now-I'm in too much pain. But yes, of course, there were good things," he admitted. "I'm not stupid. But we conceded two goals from 35 metres out. Congratulations to Brighton. We're suffering."
"I'm going to be frustrated. I'm not a robot-I'm human. I put everything into this. Naturally, I'm upset. I come here and try to speak calmly, but inside it's a different story."