Coins like, Ethereum, litecoin, Xmr, Bitcoin achieved success because they are good projects.
agree with that, also if you're a developer of a project, you should put a timeline on your goals so that participants know if its still worth it to hold or not. you should also do forecasting but it depends because we all know that there's always a sudden changes when it comes to value of coins. a project tagged as success if it completed on time and budget, with all features and functions as specified so basically putting a timeline is important, and Those failed projects were abandoned or cancelled at some point and thus became total losses.