My father's birthday is 28th February. I think of him a lot, but especially on that day. I have been blessed by reading John Piper's loving words at his father's funeral. He had a father worth honouring!
In the link at Desiring God, there is also a great tribute Piper preached on his father's 80th birthday.
I hope reading these articles encourages you, as it has encouraged me, and I hope you will honour your father, and tell him you love him, if you are fortunate enough to still have him. My dad died in 1995, so I can thank God, but not dad himself.
If your father is highly flawed, is there anything good you could say about him? Is there anything you could thank God for? You don't have to lie about his faults, to express gratitude for his good points.