fivehundred'eighty

The most selfish one letter word - I - avoid it.
The most satisfying two letter word - we - use it.
The most poisonous three letter word - ego - kill it.
The most used four letter word - love - value it.
The most pleasing five letter word - smile - keep it.
The fastest spreading six letter word - rumour - ignore it.
The hardest working seven letter word - success - achieve it.
The most enviable eight letter word - jealousy - distance it.
The most powerful nine letter word - knowledge - acquire it.
The most essential ten letter word - confidence - trust it.