Son came on in the second-half to seal the victory against West Ham.
Son praised his team for digging deep to defeat West Ham, saying he was pleased with Tottenham's second-half performance.
Tottenham beat West Ham 2-0 on Sunday at the Tottenham Hotspur stadium to move back into the top four.
Spurs back in Champions League places
Emerson Royal put Tottenham in front in the 56th minute of the game before Heung-Min Son sealed the victory in the 72nd minute.
The first-half, as has become the norm for Tottenham, was a drab affair, with Tottenham looking uninspired, but Heung-Min Son has attributed it to the difficulty of the Premier League.
He believes it is not easy to come out of the break a more convincing team as his team managed to do, lauding the effort.
"We can stay here all day talking about performances, the Premier League is really really tough and it was a tough game and tough result,” Son told the BBC.
He also admitted that scoring the first goal made things easier for them as the game opened up and West Ham sought an equalizer.
“Coming back, the first half it is not easy to bounce back strongly so I think we did alright and obviously the goal in the second half changed everything and made the space bigger and create chances and that makes a huge difference so we score the first goal which is really important and we did that early in the second half.
“Happy for the second half performance and the effort that the lads but in and I think well deserved for the team."
Son on starting from the bench
Richarlison replaced Son in the starting line-up, and not for the first time this season. The Korean admitted it was not something he was pleased with, as is the case with every footballer, but he said he is always ready when the team needs him.
Son also revealed that anytime he starts from the bench, he watches the game, evaluating how he can help his team.
"Every player doesn't want to sit on the bench, this is clear but when I am sitting there, I'm always thinking where I can help the team and that's what I did when I came on. Today was a difficult game, we make a clean sheet and score the goals so I am very, very happy today.
Son also spoke on his personal development, saying there's still so much room for growth and improvement in his game. He said playing badly only inspires him to want to do better next time.
"I still want to improve, I still want to do better things that I haven't done, I'm always always positive after I play bad so I don't want to celebrate too much after the victory. With my performance, I know I can do much much better and I want to improve.
Tottenham play in another derby next weekend when they host Chelsea at the Tottenham Hotspur stadium.
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