This phrase is often used as a metaphor, which means if you want to find what you are looking for, you should not give up easily but keep trying. It means that you need to accept possible rejections, meet several people, and make a lot of efforts before you can find the right person that you’re looking for. The phrase compares the long process of searching for the right person to kissing frogs, namely, you must kiss a lot of frogs before you are lucky enough to find the prince.