While Onyeka has played an important role for Nigeria over the last few years, the midfielder has struggled to break into the starting line-up at Brentford.
He is yet to start a Premier League game this season under new manager Keith Andrews and spent the previous campaign on loan with Augsburg in the Bundesliga.
The 27-year-old says he worked on his mental preparation during his time in Germany, adopting mindfulness techniques.
“It’s good because if you’re stressed, you just try to be calm and relaxed as much as possible,” he revealed.
“I try to do that every day, but most times I do it before games, just to prepare myself.
“I do it in my room before I go to the stadium and after the first half I try to do a bit. I just focus on my breathing to make sure that I feel settled.”
While Onyeka played more minutes with Augsburg, he failed to find the target in 34 appearances in all competitions.
But his goals were key to Nigeria’s bid to reach next year’s World Cup, scoring in the 91st minute against Benin to take his team into the play-offs, before also netting in the defeat to DR Congo.
“I’ve been looking to get goals into my profile,” he said.
“In my time in Augsburg [it was] something that I discussed a lot. I always want to go forward, I want to score goals.
“It’s sad that we didn’t qualify for the next World Cup, with the talent that we have. It’s a motivation for us to go into Afcon and win it and bring it back home.”