Humility and modesty are important in life because they allow for a realistic self-perception, fostering better relationships with others by promoting empathy, openness to learning, and a willingness to help, while also preventing arrogance and allowing for personal growth by acknowledging one's limitations and appreciating the contributions of others. Having said that, the absence of these qualities may have some adverse consequences.
Our ancient Sanskrit transcripts has following to say :
रूपं विद्या धनं धर्मोSप्यफलः स्याद्विना तु यम्|
विनयोSसौ न कैर्वात्र सम्पाद्यः स्याद्धितेषुभिः||
Roopam vidyaa dhanam dharmopyaphalah syaadvinaa tu yam.
Vinayosau na kairvaatra sampaadyah syaaddhiteshubhih.
Roopam = appearance.
Vidyaa = learning, knowledge.
Dharmopyaphala = dharmo + api + aphalam.
Dharmo = religious austerity.
Api = even.
Aphalah = futile, fruitless.
Syaadvinaa = syaat + vinaa.
Syaat = perhaps
Vina = withour,
Tu = but, and.
Yam = self-restraint, suppression.
Vinayosau = vinayo + asau.
Vinayo = humility, humbleness.
Asau = exist
Na = not.
Kaih = what,
Waa = how
Atra = here.
Sampaadya = accomplished. Syaaddhiteshubhih = syaat + hiteshubhih.
Hiteshubhih = well wishers.
Appearance (beauty), knowledge and learning, wealth and religiosity without self control, all these are futile, unless a person has modesty and humility. Therefore, persons who crave for their welfare, should be humble and modest in their behaviour.
When someone lacks modesty and humbleness, it can negatively impact their life by fostering arrogance, hindering their ability to learn and grow, damaging relationships, making them less approachable, and potentially leading to poor decision-making due to an inflated sense of self-importance and disregard for others' perspectives. So better we stay grounded and focus on life.