We have narrations that the Prophet Muhammad (SAWA) used to fast on Monday because it was his birthday in the week. ( Saheeh Muslim, Hadeeth number 1162). Celebrating our birthday should be in this prophetic way to thank Allah (SWT) that He created us and thank His great bounties on us. Celebrating of birthday should not make the person feel proud or think whatever he has is because of his own smartness forgetting the real source of all bounties, Allah (SWT).
Celebrating our birthdays must be thank giving and practicing humbleness. Fasting is a very good way to thank Allah Who created us as well as giving charity and being more nice to our parents and relatives.
'Wassalam.