Everton won 2-1 as Dwight McNeil struck twice after Marc Guehi had given Palace the lead.
Glasner said afterwards: "Big disappointment, especially because I think we lost the game with mistakes.
"Over 70-75 minutes we controlled the game but you must be focused all game. It is a big strength of Everton's in set-plays. They do it well and we defended it most of the time really well. It was always the second phase. It is important to always keep your focus high.
"We tried everything, we changed the system, brought on all our offensive players. They defended with 10 players around their box so we didn't have a lot of space so it was difficult. Today we couldn't score the equaliser. If you concede two goals it's not so easy to get a point or to win."
On still waiting for a first league win this season, the Austrian added: "We know it when we look at the table. Maybe it is a welcome back to reality. Maybe we were flying too high after a great finish to the season. The Premier League is a fight."