Sometimes this phrase is used in a military context.
Other times it’s used more to refer to a moral position on something.
Either way it means taking a decision that will make you stronger. It means putting yourself above the fray, real or imagined. It means choosing the path that will hopefully give you some advantage in the present, and maybe the future too.
Keep your sense of what’s right, what the best decision is for you and your situation.
Remain strong. Don’t allow yourself to lose your dignity, your humanity. Take the high ground and hold it. You’ll be glad you did.