"Neither politics nor the AfD are without alternative for me," Petry, 41, told the Berlin daily Tagesspiegel.
"It's a good idea to reassess your own life from time to time and to readjust it," she added.
"That's what I'm doing now, after more than four years in the AfD which have required an enormous effort and meant saying goodbye to a normal life," said Petry, who is currently pregnant with her fifth child.
Petry joined the AFD shortly after its founding in 2013 and later led a coup against the eurosceptic economics professor who founded it, Bernd Lucke, to take the party further to the right.
The small protest party surfed a wave of angst and anger over Germany's mass refugee and migrant influx that peaked in 2015 but has recently slipped in opinion polls into single digits as arrivals have dropped sharply.
Petry sparked outrage during the crisis when she suggested that as a last resort, guards should be allowed to open fire at migrants streaming into Germany.
She has voiced strongly anti-Muslim views and linked up the AfD with far-right European leaders such as France's Marine Le Pen and Geert Wilders of the Netherlands.
In recent months, she has weathered fierce attacks from foes inside her party in the lead-up to September general elections, and photos of Petry bursting into tears at a party meeting last weekend were widely published by German media.
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