I had a good time at Chelsea and was accepted in the team, so it's difficult to explain why I left. My performances were good as well, but there was a time in my second season when I felt I didn't have the manager's trust any more and I didn't play many matches from the start.
I definitely did not fail at Chelsea. I always had my chance, scored important goals in the first season. At the end I just wanted the transfer, although Jose Mourinho wanted me to stay.
I love Chelsea still. I'm not frustrated; it was a great experience.
I don't think you would find any player in the Bundesliga who would say that they would not at all be interested. Chelsea would have been very interesting for me. You don't get a chance like that very often in your life.
We need to show we could be in a fight, a battle, and win it. If that means we have to be willing to do something that takes a yellow card, then we have to be ready to do that for each other and I'm happy to do that.
I think I'm quite a clever player and that I realise there are times when I can be offensive but others when I must be more compact and work for the team, because that is what matters.
It's not that easy to come from the Bundesliga into the Premier League. It's something different.
We had a difficult last two years when I was in Dortmund. It was not easy, the relationship between fans and players.