The forward struggled for both form and fitness at the start of the season under former boss Slavan Bilic but has come good under David Moyes, with many putting his improvement down to the Scot's demand for hard work.
The 28-year-old says it has not been as simple as that and he spoke to his family and motivated himself to get going for his new club.
"When I came to Stoke, it took me six months to settle in, and the same happened here," the Austria international told the club's website.
"I didn't want this to happen, as I wanted to make an impact immediately at West Ham, but everything was going around and I was obviously in the spotlight because I came for a lot of money and didn't perform how I wanted to, or how the fans were expecting of me.
"Now, I feel fit and had a lot of talks with my family and got into myself and said: 'Let's go Marko, you need to change things, try your best and work even harder' and I'm happy things are going well and I can help the team.
"I want to keep this level and I am sure I am going to keep it if I continue to work like this."