Don't say it's easy
When teaching someone how to do something, don't say that "it's easy".
If it were easy for them, they wouldn't be asking you for help.
Even though you're trying to reassure them that it isn't actually that hard, you're starting from different places. For example, take calculus. Once you've learned some calculus, you have the mental framework, and you know what pitfalls to avoid. Someone encountering it for the first time is going to encounter problems you can't even imagine.
That's one of the things great teachers can do: mentally model what problems their students are going to run into, and nudge them to avoid those pitfalls.