Scott Doe scored the only goal of the game after five minutes when he crashed a near-post header into the back of the net from Matthew Saunders' well-flighted corner kick.
Defeat for Exeter was their third in succession and all but ends any hopes of automatic promotion. They remain in seventh, but the chasing pack are closing in with just two points separating them and Bradford in eighth.
"It was disappointing," Tisdale said. "It has been a really bad week for us and I stood in the dressing room and listened to the players have their say.
"I'm pleased they said their piece. It wasn't heated, but it was frustrated and I am quite philosophical about it. I was very disappointed losing on Monday (against Rochdale) because at this stage of the season, you are fighting for points and we were leading with five minutes to go. We lost and that was a killer for us.
"We conceded an early goal and I would like to think we'd have got it back. It was a hard ask, but the play was disjointed. Our decision making was impaired by anxiety, frustration, panic and a bit of this and a bit of that.
"It was by no means a strong performance, but there was a lot of effort. We started the game with a substitution in the first minute and it was just a very disjointed day.
"I am desperate to get into the play-offs, but we are finding it very difficult at the minute. But it's not over and we go again at Rotherham on Tuesday and we will attack it in the best way we can."