What is the surest sign that your financial decision is irresponsible?

You cannot afford to lose the money you spend or invest
The investment is in a startup company
There is a possibility of gain but also a risk of loss
The investment involves the stock market

All of the above options can be considered signs that a financial decision may be irresponsible. However, the surest sign would be if you cannot afford to lose the money you spend or invest. This indicates that you are putting yourself in a financially vulnerable position, where any loss could have serious consequences for your overall financial stability.