Why is it so common for Christians to praise God for their successes, but blame themselves for failures?
Principally because any success or failure in this life, is predicated on your capacity to hear the Lords direction. When you listen and follow directions, you will have success, when you don’t, then its on you.
For those who reflect on their failures they typically see where they disconnected from the Lords direction and typically accept responsibilities for the negative outcome. On the other hand, vice versa they see the Lord in their circumstance as they sought His direction up front and follow it, which is why the attribution and thanks for success.
That is an extreme simplification, but thats it in a nut shell.