Despite being on top for the majority of the game, a late goal from Jessie Gale on 90 minutes consigned the Eagles to their second defeat of the BWSL2 campaign.
Amber Nixon had put Pompey 1-0 up on 32 minutes, before Annabel Blanchard equalised on 42 minutes from inside the box.
Speaking after the game, Potter said: "We're hugely frustrated and disappointed. We're making silly errors and silly mistakes and it's costing us massively.
"We're not finishing our chances at the other end and we had numerous chances, especially in the first half, to really put the game to them and put ourselves in front, which we didn't take.
"They had a couple of opportunities themselves. I thought they outworked us and I thought their desire was higher than ours today. And that's what I've just told the players in that dressing room. I think it's a shame that that's something that we've questioned today.
"So we need to make sure that we're putting that right because you've got no time to dwell on it. We have got to put it right and we have got to move on fast."
