In four of the last six top-flight fixtures, Palace have dropped points during the closing stages of games and it has left the Eagles just three points above the relegation zone.
Tomkins says that it has partly been down to bad luck but admits that regardless of the reasons, Palace must improve during the final weeks of the campaign.
The 29-year-old is quoted by the London Evening Standard as saying: "We have conceded a few late goals and we are aware of that as a team. It is something we are trying hard to get out of us.
"It is disappointing at the end of the Bournemouth game. It felt like a loss in many ways. We will bounce back from that. Performances of late have shown we are a team who are capable of getting out of the position we are in.
"It might be a bit bad luck, when you look back to the Manchester United game and what a strike that was from [Nemanja] Matic. The weekend just gone against Bournemouth maybe just some concentration, it happens."
Palace can move to within a point of 14th-placed Brighton & Hove Albion with victory at Selhurst Park on Saturday afternoon.