"In for a penny, in for a pound" is a phrase that means if one is going to take a risk or commit to something, one might as well go all the way. There are several synonyms for this idiom, such as "all or nothing," "go big or go home," "if you're going to do it, do it right," and "put your money where your mouth is." These expressions convey the same idea that once one has committed to something, there is no turning back and one must follow through with complete dedication and determination. Whether it's a risky investment or a personal challenge, these phrases encourage taking bold action and embracing the potential rewards that come with it.