If the agreement is properly drafted it can be enforced by entering a judgment against you under Code of Civil Procedure Section 664.6. A breach of that agreement could subject you to damages.
You are stuck with the agreement unless the damages you face for breaching it are extremely minor.
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If the other party has not yet signed the agreement, then - assuming you provide timely notice to the other party - you can withdraw your offer to settle.
If the other party already has signed, then you may rescind the agreement only if (a) the agreement has a provision allowing for rescission or (b) the other party agrees to let you rescind.
Disclaimer: This post does not constitute legal advice and does not establish an attorney-client relationship.
Without more information it is hard to say, but you may need to also consider who drafted the agreement, and what exactly are the terms and conditions? For example if the conditions are violative of public policy they be unenforceable anyway. Generally if a licensed attorney drafted the document you are less likely to find such unconscionable provision. Likewise the mere fact that a lay person drafted the document will not be a sure bet that the provisions are unenforceable. But if your exit options are limited, it may be worth taking a look at these factors.
The true key to successful settlements is having the disputants contribute input to the resolution. By nature people are more likely to follow through on resolutions that they help define.