Karacharana Krtam Vaakkaayajam Karmajam Vaa is a famous Sloka or actually a prayer for forgiveness to bhagwan Mahadev Shambhu ie god Shiva. This bedtime Sloka is a prayer to God Shiva asking him to excuse our mistakes and maintain his mercy on us. Lord Shiva is known as the lord of Mercy and Compassion.

Karacharana Krtam Vaakkaayajam Karmajam Vaa,

Shravananayanajam Vaa Maanasam Vaaparaadham,

Vihitamavihitam Vaa Sarvametatkshamasva,

Jaya Jaya Karunaabdhe Shri Mahaadeva Shambho

करचरण कृतं वाक्कायजं कर्मजं वा ।
श्रवणनयनजं वा मानसं वापराधं ।
विहितमविहितं वा सर्वमेतत्क्षमस्व ।
जय जय करुणाब्धे श्रीमहादेव शम्भो ॥

Meaning: "O God, kindly pardon my incorrect actions done consciously or unconsciously, either through my organs of action (hand, feet, and speech) or through my organs of perception (eyes, ears) or by my mind. I adore the God, who is the ocean of kindness".

By God's grace, we have completed one more day of our life. So, in order to thank god and to ask for his mercy, one can recite this Sloka. This bedtime Sloka is a prayer to God asking him to excuse our mistakes and maintain his mercy on us.