As Nikiha Miller prepares for the U.S. National Team Trials in kayaking at Lake Lanier Olympic Park on Saturday, he can only think back to his mantra: “Change is inevitable, growth is optional.”

A top-two finish in the 200-meter kayak race could get the above-the-knee amputee a spot in the World Championships in Germany to represent Team USA, The Gainesville Times reported.

This would be his fourth time competing in the world championships.

The 37-year-old former Marine started kayaking seven years after a 2004 motorcycle accident that left him with a crushed hip, ruptured aorta and without a right leg.

“A friend of mine brought it up as an idea,” Miller told the paper. “It was slow. The adrenaline junkie in me wanted to go faster.”

Since then Miller has competed on the national and international level. Still, there are days when his strength is challenged.

“There are a couple of down days,” Miller told the newspaper. “But then you realize that makes for a long day. You can either be upset about things that you can’t do anything about or you can figure out ways to make do with what you have.”

Miller has a chance at competing in the Paralympics in Rio de Janerio this summer, but told the paper 2020 is more realistic.