عَلَيكُم بِالفِكرِ فَإنَّه حَياةُ قَلبِ البَصيرِ وَمَفاتِيحُ أبوَابِ الحِكمَةِ. Don`t ever regret deep reflection and rationalisation, for thinking revives the alert heart and is a key to doors of wisdom.
Bihar al-Anwar, Vol 78, page 115
Imam al-Hasan ibn Ali al-Mujtaba (peace be upon him)Hadith