"If I am here for one more term, my kids will only ever have known me as a weekend dad. I can't let that happen," the 48-year-old Wisconsin Republican told reporters.
Ryan, who has been in Congress since 1999, will serve out the remainder of his term and leave office in January. The congressman cast it as a personal decision to see more of his teenage children before they are fully grown.
The House speaker said believes he "achieved a heck of a lot" as speaker, a position he accepted reluctantly. He highlighted the Republican tax law passed in December and the massive increase in military spending signed into law last month as his biggest achievements.
Some reports indicated President Donald Trump's behavior had been taxing for Ryan. The GOP also faces a tough fight to keep the House in November's midterms amid Democratic enthusiasm and opposition to some policies pushed by Trump and the Republican-controlled Congress. The speaker's move raises the prospect that more GOP lawmakers could decide not to run for re-election.
Ryan told reporters the prospect of Democrats taking the House majority in November had no bearing "whatsoever" on his decision not to run. He also believes his retirement will not have an effect on Republicans' ability to keep their seats.
"I really don't think a person's race for Congress is going to hinge on whether Paul Ryan's speaker or not," he said.
Ryan argued that the GOP has a "great record" and "great economy" on which to run. Republicans have used the tax plan as one of their main arguments for why they should hold the House, though it is not clear the policy has resonated with voters.
The House speaker said he knew holding the position would be "fleeting," and added he did not want to let it take over his life.
"It's easy for it take over everything in your life and you can't just let that happen. Because there are other things in life that can be fleeting as well," Ryan said.