schieffer symposium was speaking to students at an annual symposium that bears his name at texas christian university 's schieffer school of journalism in fort worth , his alma mater .
it 's not his first retirement announcement but , at age 78 , looks like it has a good chance of sticking .
` it 's been a great adventure , ' schieffer said at the college .
` you know , i 'm one of the luckiest people in the world .