Sounds like there's a communication issue between you and whoever is holding you to this deadline. You should have a week of buffer at least. If you think you're coming in hot, notify whoever ASAP that the deadline needs to be extended and/or more resources need to be allocated to your project. If neither are possible then escalate the issue higher up. It's there's still no action, miss the deadline, it's ok to let the ball drop if you can't handle it. Don't stress it either. It's a signal to the company of a larger issue, especially if it's documented that ample notification was given. It will be the person that held the deadline that will be ultimately be responsible for not working with you to resolve the situation.
You are part of a company/team, if you're soloing basically anything without support that's a red flag. Don't take failure personally, if you've done everything correct and communicated properly any failure is the team, not just you. I used to be in your situation. You need to change your perspective and detach any personal responsibility. Do what you can, and if you can't communicate. Failure is an option, but don't view it as yours. If you think things could of been done better, people should of listened, save it for the retrospective.