Breaking Engagment S.O.S

Hey Ladies! I could really use your support. As hard as it is for me right now. I am planning to break my engagment of 1.5 years before we invest too much money in to the whole thing. I attempted to break it once, but this second time around I plan to be much firmer. I have collected my thought about telling my SO that I don't feel like we should get married, but I am not sure how to rip of the bandaid about breaking our 8 year relationship too. This has nothing to do with another person. I just feel excited about the engagment, have had numerous doubt, don't really see a positive outlook for our future, and I am starting to consider the rigid mindsets that will never change and that do matter when entering a life-long commitment. Our foundation is not solid. Sure I could go to counseling, but that is just buying more time to still end in disaster. That is time I could have spent being happy, in what ever that entails. How do I break the engagment and the relationship off without ambiguity(?)