A safety plan is a critical part of treatment for borderline personality disorder (BPD). People with BPD are among the highest risk of attempting suicide, or engaging in other high risk behaviors. Without a safety plan, you may be in danger of harming yourself or someone else. A safety plan can reduce your risk and make it less likely that you will make a decision in the heat of the moment that will have serious consequences.
If you have BPD, you should develop a safety plan now. If you care about someone with BPD, ask them whether they have a safety plan, and if they don't, encourage them to work on one.