Following a strong start to the campaign, with Di Resta finishing in the top 10 in seven of the opening eight grands prix, the subsequent races in Germany and Hungary were a nightmare for the team.
Neither Di Resta nor team-mate Adrian Sutil collected a point, with one of the key issues being Pirelli's change in tyres following the blowouts that occurred during the British round at Silverstone.
Traditionally, Force India have been strong at the next two races in Belgium and Italy, with Di Resta looking to Spa and Monza to pick up the pace again.
"I don't want to let this championship get away from us," said Di Resta.
"We started off really well and there is no reason why we can't keep doing that.
"We have missed some opportunities lately and that allowed our rivals to close in, but I have faith in the team and I know everyone is working hard for the races ahead. We need to get the car working for us like before.
"In Budapest it was difficult to drive, but sometimes you get those tough weekends.
"Since then we have regrouped and analysed the previous races properly and hopefully this weekend will be a fresh start.
"We usually do well in Belgium and everyone is determined to get back to the situation we had at the start of the year when we seemed to be punching above our weight."
Team principal Vijay Mallya recognises the tyre dilemma is a concern, although has suggested time is required to solve it.
"Tyres have played a very important role this year from race one onwards," said Mallya.
"We were on top of the tyre game up until Silverstone and then in Germany and Hungary we struggled with the new tyres.
"We need to get on top of that and there's no reason why we shouldn't be able to. We just need time, and I'm quite optimistic we will come back strong."
Mallya can only hope that is sooner rather than later, adding: "If I concede that Hungary was not ideally suited to us, by the same token Spa and Monza have traditionally been our stronger tracks.
"So that gives me a little bit of a morale boost in saying once we are on top of the game, we should restore our competitive position."