Humility doesn’t mean that you have to let people ‘run all over you’.
It doesn’t mean that they have a right to demean or belittle you, your knowledge, your experience, your character, who you are…especially just to feed their ego, or sense of pride.
It’s not a sin to assert yourself as long as you do it in a Godly manner.
Look at what Job said when his friends, who were supposed to be there to comfort him, began to blame his troubles on him…
Job 12:3 (NKJV)
3 But I have [a]understanding as well as you;
I am not inferior to you.
Indeed, who does not know such things as these?
So, if someone expects you to feed their ego by belittling you, here’s some help if you ever can’t think of what to say…
I respect you. But, I lick my lips too many times a day to kiss your butt.
It’s not a sin to assert yourself!