You're Late! Now What?
If you realize that your project is going to be late, do not despair. Try to keep calm, after all you are not the first nor will you be the last project manager to miss a deadline. Anxiety will only make things worse.

Now that you have calmed down, the first thing to do is to analyze the situation. Do not do anything before this analysis; as the project progresses, things could get worse.
Ask for help. As a project manager, you can (and should!) ask for all the help you need. A good alternative is to ask for help from someone outside of the project, preferably someone higher in the hierarchy, such as a department manager or director who can help you assess the situation more clearly. Often times, an outsider tends to perceive minute details and might be able to detect some weak point that passed unnoticed by you or the project team.
Once the situation has been evaluated and all problems have been detected, you should create a new timeline and communicate it to the stakeholders. According to the PMBOK, project managers should spend 90% of their time communicating. Besides, negotiation is one of the main skills a project manager should have.
So this is the right time to start using that skill. This is the time to negotiate a new deadline with the client, but make sure the result of the negotiation is good for all parties. Remember that you will not have much chances to start a new negotiation, therefore, all aspects of the project that need to be renegotiated should enter the discussion right now.
Have a nice work day!
