Lewis Hamilton hinted at trouble away from the track, and said he was "only human", as he spoke for the first time about the social media backlash which provoked him to write that he felt like "giving up on everything".
Hamilton arrived in Mexico for Sunday's race, which could see him crowned a six-time world champion, facing criticism for a series of Instagram messages in which he took aim at the state of the planet and agriculture farming, while encouraging his 13 million followers to follow him into veganism.
The British driver's comments led his former team-mate and retired double world champion Fernando Alonso to say: "I think I would keep my eating habits to myself. We all know the lifestyle that Lewis has, and that Formula One drivers take 200 planes a year. You can't then say 'don't eat meat'."
"Like everyone, I have up and down days", said a clearly wounded Hamilton. "It is very difficult for people who watch on social media to be able to relate to certain individuals who live in a celebrity world. They have feelings.
"Some people care about that, some people care less, so it wasn't the best feeling at that moment.
"I have great people around me, and I have had a lot of support from my family and friends. Fortunately I am not alone. There is a lot going on in my life at the moment."
Hamilton was asked about his final remark, but refused to elaborate.
"There is a lot that goes on in our lives," he added. "It is important not to hold things in. I am always open and very transparent with my feelings, whether people like it or not.
"Coming into this weekend, I feel very positive and I am back to what I love doing. It is about trying to be positive which is not always easy."
Hamilton then laid out his green manifesto, revealing he wants to be carbon-neutral by the end of the year.
The 34-year-old said that he doesn't allow anyone in his house or office with any plastic materials. He added that he has reduced his travel by plane, and sold his private jet last year.
Hamilton has also called on his Mercedes employers to ditch the all-leather interiors in their road cars. He added that his Tommy Hilfiger fashion line is made from 70 per cent sustainable materials.
"It is important to feel like you are doing something positive, regardless of those who try to knock it down," he continued.
"It is not the easiest because we are travelling around the world and our carbon footprint is higher than the average homeowner. But that doesn't mean you should be afraid to speak out for positive change.
"I am looking at how I can improve and the effect I have on the world. It takes a while and it is not a quick fix."
Hamilton will move to within one championship of Michael Schumacher's all-time record if he outscores Mercedes team-mate Valtteri Bottas by 14 points here in Mexico City on Sunday.
But Hamilton's Mercedes team have struggled for pace at the high-altitude venue in recent seasons, meaning that the Briton may have to wait until next weekend's US GP before he is crowned champion of the world for a fifth time in six years.
"I don't remember any point this season where I have finished 14 points ahead of Valtteri," he said. "It doesn't matter where it is done, as long as you get it done.
"I am super-focused on the remaining four races. I am fully aware that there are plenty of points available so I have to deliver."