How is Current Account Deficit Harmful?

A large current account deficit may imply that the economy is relying on consumer spending and is becoming less competitive. This will further lead to lower growth.
It leads to lost confidence of the investors. The risk of investors will take their investment out of he economy and cause devaluation further lowering their confidence.
A current account deficit would imply surplus in capital account so as to balance the BoP. This implies that there is increasing claim by foreigners on domestic assets. This may lead to reduced long term income.
A current account deficit which is financed through borrowings is said to be unsustainable as in long term, country will have to repay the debt and interest payments.