""Recompense to man man evil for evil. Provide things honest in the sight of all men." Romans 12:17
Defending yourself is not the same as vengeance. I've heard so many interpretations about people protecting themselves and the naysayers use verses like this to show how we should just lay down and let others walk on us, steal from us, cheat us, or worse. That is not the spirit of this verse at all. Defending yourself is not an offensive act. If after you have been hurt by others you make a plan to get back at them and do them harm then you are recompensing evil for evil.
Vengeance is mine sayeth the Lord.
The point of this verse and the whole of scripture is for you to recognize your part in the big picture and recognize what part God has in the big picture and carefully work within the parameters of a godly life to enjoy your life and bring blessings into other's lives. All of this under the guidance of the Holy Spirit and all of this understanding your part in it. God has a plan for His people to be set apart from the mind-set as the world and to live out the experience of having the indwelling Holy Spirit.
Be yourself and don't put on a front. Let people know you are real and that you care about them. Do what you can for others while you are growing. Don't take something that is not yours and live within your means. This is good advice. "Provide things honest in the sight of all men."