In that case, it does pay off to double down. If the odds are in your favour it's a different story.
If the odds are against you in a game, you're more likely to lose double your money than you are to win it back.
If you bet on the roulette ball landing on 1 and you lose, it doesn't increase your chances of guessing right the next time. This isn't true - at least, not in most games of this kind. If we lose a bet multiple times, it increases the proablility of winning the next time.