Will Knight admitted Havant’s 33-31 defeat at Cobham handed the initiative back to Tunbridge Wells in the race for the London one south play-off spot.
A last-minute penalty condemned the visitors to a damaging defeat on Saturday.
With just two games left to play, Havant still hold a three-point advantage over their Kent rivals.
But the Hooks Lane outfit are facing a much tougher run-in.
‘We are certainly not making it easy for ourselves,’ said Knight.
‘It was a hugely-frustrating afternoon for us where we failed to finish things off.
‘Knock-ons and missed tackles kept allowing our opponents back into the game.
‘Cobham also played like a team with no pressure on them, while we were nowhere near precise enough.
‘Sooner or later you can’t keep riding your luck without coming unstuck.’
Havant trailed 17-12 at half-time after opening the score through a Mitch Goldring try.
Darren Bamford scored Havant’s other first-half try following an excellent break by Joel Knight.
Jerome Rudder levelled the scores early in the second period before the home side stretched into a 30-17 lead.
The visitors, however, hit back.
Darren Bamford scored his second try and there was another from Loz Blackburn seven minutes from the final whistle.
In the final minute, though, Havant were penalised for handling on the floor.
And Cobham took full advantage – knocking over the match-winning penalty to break Havant hearts.
‘We know exactly what we have to do,’ added Will Knight.
‘It is still in our hands but we have two massive games left to play.
‘Our final game of the season is at leaders Sidcup, so it isn’t going to be easy.’
Meanwhile, Tunbridge Wells stormed to their expected 52-5 bonus-point win at Gosport & Fareham.
Barry Bridgman was left rueing a slow start by his Gosport Park team.
‘The first 25 minutes was dreadful but we improved after that,’ he said.
‘I was quite proud of the way we played in the final hour of the game.’
United Services face a final-day London three south west relegation shootout at Millbrook after suffering a thumping 71-0 home defeat at the hands of Basingstoke on Saturday.
Services hold a five-point lead over Millbrook but have an inferior points difference.