The word "stupid" carries a certain weight within human consciousness. 'Stupid' is what you "call" someone, how you "judge" and label them. It comes with an emotional reaction, usually annoyance or frustration. How we tend to use and experience the word "stupid" is as a mental/emotional attack. It's something we dish out to others when we believe they 'deserve' it and something we try to avoid being labeled as ourselves.
When you're called 'stupid' you feel humiliated, shamed, rejected, diminished and inferior. It makes you feel like you're not good enough and are 'less than' for lacking a certain skill, ability or expression. It's an experience we fear facing and so we'll find ways to hide or avoid those parts of ourselves we've come to judge as 'stupid'. Maybe you've never developed the greatest social skills. Maybe you were never good at math or languages or have a hard time retaining and remembering facts. In order to avoid the label "stupid", you'll tend to stay away from doing things that might expose your inferior ability to others. We've come to create quite an emotionally charged relationship with the word 'stupid'.
The word 'stupid' can be used in a supportive way however. This word isn't just a judgment. It's a word that exists within you in connection with aspects and parts of yourself which you know are weaknesses or underdeveloped abilities. So, whenever you judge yourself as stupid or fear to be judged that way, then it's an indication that there is in fact something within and about yourself that you should give a bit more attention to. It's pointing towards a part of you wherein you've held yourself back or suppressed yourself in your development.
When you take the emotion out of it, you'll realize that the word stupid is actually part of living the word 'intelligent'. To be intelligent is to be honest with yourself about your shortcomings and weaknesses and to assist and support yourself to learn, grow and expand. In order to live the word intelligence it is essential to be open and honest with yourself about those parts of you that are stunted or 'stupefied' so that you can grow and expand from there.