Paraphrasing: The snow began accumulating slowly. One inch, then it was two inches, before you knew it there was 1/2 a foot of snow, then a foot, and a second foot, until an entire metropolitan center became completely paralyzed. Venial sin is just like that snow. Before you know it, you are paralyzed and trapped under a pile of sin.
One of the most important elements of Lent is penance. There honestly isn't a better way of addressing this detail than going to confession. If you haven't gone yet, it isn't too late. Do your soul a favor and get shoveling!
"If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness." 1 John 1:9