Mid-table QPR went in front on the stroke of half-time when Lyndon Dykes slotted home his sixth goal of the campaign from close range.
Sixth-placed Reading secured a point, their first home league draw of the season, thanks to Yakou Meite's scuffed effort early in the second half.
"We created a lot of good moments in the game, a lot of good chances," Paunovic said.
"But I feel as if I am having to repeat myself. We create so many opportunities and we just don't execute properly.
"We can't afford this, whether in the Championship or in the Premier League – or even in the Champions League or the World Cup.
"To miss so many big chances, when it is not easy to create them – we have to be better at this.
"We have to connect that final part, the execution, especially moving into the final part of the season. It's going to be crucial.
"I thought it was a good game and we played against a very good opponent. I'm not really happy with the draw but I also think that there were a lot of positives in our game.
"I'm happy with the spirit, I'm happy with the way that we reacted to their goal.
"We were a different team in terms of our mentality in the second half. We put our foot to the bottom, we put our pedal to the metal, and it worked.
"But we go back to those big chances again. Had we taken them, it definitely would have changed the outcome of this game."
QPR have lost only once in five Championship matches.
"We got the goal just before half-time, which was good, but we got a bit sloppy for the first 15 minutes in the second half," Rangers manager Mark Warburton said.
"We then conceded a goal that we just can't concede. There was a challenge and we just had to defend it better.
"But then we came back into it, got into it much better and probably dominated the last 20 or so minutes. We then created quite a few chances against a very good Reading team.
"I suppose the overall feeling is one of disappointment. But to come to a place like Reading and be disappointed with a point, that means you must be moving in the right direction."
Warburton was also pleased with the first goal for Dykes, the Australia-born Scotland striker, since late November.
"I thought that Lyndon did well, with all his movement and making some great runs from outside to in," he said.
"He got the goal and again worked tirelessly today. He also had a good game in midweek (in the 3-2 home win over Millwall) and I'm sure that he'll now go off with the Scotland squad full of confidence.
"I'm sure he'll also be looking forward to a very strong end of the season.
"He was probably lying around on a beach five years ago and now he's playing at this level in the Championship – and now with Scotland.
"It's like another world and it has happened so quickly but I'm very pleased for him."