作践 carries strong negative emotion, to humiliate a person or to spoil something through carelessness or contempt. The pronunciation 作 here is zuò (also heard as zuó in colloquial speech). Common reflexive use: 作践自己 ('to degrade oneself / waste one's potential').
register
Colloquial and somewhat northern. More formal alternatives: 糟蹋 (zāotà, to ruin / abuse), 侮辱 (wǔrǔ, to insult / humiliate).
