Why we do 'Shri Ganesh' (श्री गणेश) before any new beginning....

Swastik Chinah

ॐ गं गणपतये नमः॥ 
Lord Ganesha is one such God who is worshiped in the beginning of every prayer, yagna, religious ceremony and even new things are welcomed with 'Swastik' symbol which is drawn on using red sacred powder (KUMKUM). As per hindu tradition, devotees also wear yellow and orange 'kumkum'. Now the question arises....

Why every celebration is commenced with Lord Ganesha's prayer or worship?

Shri Kaal Bhairav Gayatri Mantra

Bhairav Gayatri Mantra:

"Om Kaalakaalaaya Vidhmahe,
Kaalaatheethaaya Dheemahi,
Tanno Kaala Bhairava Prachodayat॥ "

In hindi,

"ॐ कालाकालाया विधमहे,
कालाअथीथाया धीमहि,
तन्नो काल भैरवा प्रचोदयात॥"

Shri Krishan 56 (chapan) bhog, legend (katha) behind this.

Shri Krishna is known to be Eighth Avatar of Lord Vishnu. He took this Avatar in Dwapar Yug in Yadav clan and known to be a Yadovanshi. He is fond of Cows and so got the name Gopal, Gwalpal. He was born to Devaki and Vasudeva, who belong to Mathura (Mathura district, now in U.P). His foster parents were Yasoda and Nanda. His elder brother is Balaram (seventh son of Devaki and Vasudeva but Rohini, first wife of Vasudeva gave birth to him due to transferring of womb). His younger sister is Subhadra, born to Rohini and Vasudeva. 

Govardhan puja is done a day after the Diwali. This day is dedicated to Cows and Krishna in rememberance of this incidence.