President Thein Sein at the press briefing: AP BY YADANA HTUN, Associated Press, April 14, 2013 YANGON, Myanmar - Myanmar's president said Sunday his country needs to learn from the violence and instability that has wracked the Southeast Asian nation over the last two years if it is to overcome the challenge of democratization. Thein Sein spoke in a radio address broadcast to mark the start a day earlier of a traditional New Year holiday that is celebrated by revelers across Southeast Asia with friendly water fights. Thein Sein, a former general, took office two years ago after Myanmar's long ruling junta stepped down. He has since led an unprecedented transition toward democratic rule, releasing political prisoners, easing censorship and signing cease-fire deals with all but one of the nation's rebel groups. But the country has also been plagued by a war with ethnic Kachin rebels in the north, sectarian violence in western Rakhine state, and an