India were expected to take the series and were boosted by the fact all three games were played on pitches that suited their side, but they could not get over the line.
The team were without the injured Rohit Sharma, who will be captain when he returns, but were otherwise close to full-strength.
"Our shot selection has been poor at times and with the ball we haven't been hitting the right areas consistently enough," Rahul said after their agonising four-run loss in the third game at Newlands on Sunday.
"That's why we ended up losing the series. We need to try and understand how we can get better as a team."
India looked flat at times in the series, though that may have to do with the stifling heat all three games were played in, but Rahul does not believe the players can be questioned for their attitude.
"I can't fault the boys for the passion and the effort. Yes, in terms of skill and understanding ,the situation of the game, sometimes we have gone wrong - but that can happen."
He believes what is important now is for the team to regroup and take stock of the series loss, and make changes where they feel it is necessary.
"We kept making the same mistakes but it is early on in our journey to the World Cup.Â
"So we must go back (home), have some hard conversations and look at ourselves in the mirror to see where we can get better."
