One who is full loathes honeycomb, but to one who is hungry every bitter thing is sweet.
Proverbs 27:7 TLV

People who think they are enough or have enough give up trying and they miss out on many good things in life. Ambition is just another word for motivation, and a little deprivation and hardship will motivate someone to improve himself, work harder.

This can be interpreted in the opposite direction also. If your heart and life are full of healthy, fulfilling relationships and activities, it is harder for temptations to find a hold on you. It's not enough to avoid things that bring temptation. You need to fill those gaps with things that bring true happiness.