all your glorious achievements are in vain if you boast about them.
'vain' means thinking too highly of oneself; so 'vainglorious' means one feeling glorious about oneself
vainglorious : BOASTFUL jab se Yuvraj Singh ne 20-20 me glorious kamgiri ki hai tab se woh bahut zyada vain [extra]glorious ho gaya hai.
vain= unsuccessful. glorious=magnificent, greatness. making false glory. meaning boosting and self concieted