What was the cause of the War of the Roses?

The cause of the war was that King Henry VI who was from the Lancastrian's branch  became to sick to rule, so his cousin Richard ran for him, but he was from the York's branch. I would hate to be royal it doesn't seem fun at all. Too years later Henry got better and so he asked Richard to give him back his power but he said "no". So the York and the Lancastrians begin to fight over power.