Why ?

Humans are never contented with what they have in life. Why is that so? I'm still searching for the answer. And why can't we learn to be contented with life? Are we just programmed to be like that? Or being contented is just too subjective? Lets see. I always wanted a pair of Converse. Now that I finally have one, I want another pair. Why?? Okay, lets see it in a non-materialistic perspective. When your period's not coming at the right time, you will say : Shit lah. So long still haven't come one ah. When it finally comes, you'll say : Ish. So farn lah become a girl. Always also bleed. YOR! So, am I the only one that is learning to be contented with life or are you all out there facing the same problem as I am? I find it really hard at times because maybe most of us are very lucky to be borned in an average, upper middle class or even of a higher class family. I feel we are blinded by ka-chings. Anyways, I just found out about this book - The Monk Who Sold His Ferrari . Maybe it can answer my ample questions about life?