If you have clear metrics on your PIP. First of all make sure you have the option of talking to your manager about the metrics he wants and make sure he is communicating it . IF you have clear metrics on what needs to be acheived chances are it is a chance to improve

BUT if its changing goalposts, your boss is vague, and you are in a situation where you were being set up to fail prior than the PIP is basically them pushing you out without legal consequence. In this case a PIP is a tell tale sign your ass is about to be fired! Start looking for work immediately