Sunan Ibn Majah Book 33, Hadith 163
the Messenger of Allah said: "Whoever persists in asking for forgiveness, Allah will grant him relief from every worry, and a way out from every hardship, and will grant him provision from (sources) he could never imagine."
the Prophet (saas) said: "Glad tidings to those who find a lot of seeking forgiveness in the record of their deeds."
the Prophet (saas) used to say: "Allahum-maj'alni minal-ladhina idha ahsanu istabsharu, wa idha asa'u istaghfaru (O Allah, make me one of those who, if they do good deeds, they rejoice, and if they do bad deeds, they seek forgiveness)."