How to access route after certain controller call

I have two routes

Route::post('checkout','CartController@billingSave');
Route::get('success','CartController@billingSave');

So after completing the billingSave method it will redirect to success page.. But if put /success also in url it shows the success page also..though he didn't complete the payment..is there anyway i could let access only the success url after completing the billingSave functionality?

means he can't access success url instead of completing the billingSave method ..or like don't give him access the success url?

via User57