WASHINGTON - White House spokesman Sean Spicer said on Wednesday he was personally and professionally pained by his comments comparing the atrocities of Syrian President Bashar al-Assad and Adolf Hitler, saying he had made a mistake and let down the president."I made a mistake. There's no other way to say it. I got into a topic that I shouldn't have and I screwed up," Spicer said during an event at a museum in Washington. "I hope I showed that I understand that I did that and that sought people's forgiveness because I screwed up."Spicer said his comments were professionally upsetting because President Donald Trump had had "an unbelievable successful couple of weeks" and it was his job to amplify that message of accomplishment but "I've let the president down."