Saying no can be difficult in a professional setting especially if you are new and your boss wants something. Managers that haven’t really programmed will keep trying to push new features or push frivolous features that takes a long time. There were time in my work where managers were pushing for extra features that ended up being not used by the end of the product cycle. Problem with is, unless you have some experience, you probably can’t say no.
This ties into deadlines, saying no can be hard especially if you are new. However, many people expect you to run into issue when you first start up and it does not hurt to ask. It is better to be delayed than write bad codes that will run into issues in the future. Unless it is a crunch time, then you have to get it done.