Roulette is a game of luck and chance, so really there is only 1 aspect of the game that you can control... The money, you can only control the money, the spinning of the wheel and where the ball will land next is not up to you. You must fully understand this idea in-order to be a successful roulette player, read on to find out how it will benifit you.
Run the roulette game like a business:
In business you have to set budgets and targets, and a good business man knows that no-matter how rich they are, they'll never have an unlimited amount of money.
So this is what you do, set budgets and targets for your game. Your target for profit should be achievable but yet slightly ambitious, and a you could also set yourself a goal to improve on your last winning session, after all this is what businesses do when they hit a target they'll raise it for next time.
Now you need to set a budget, this will be your maximum loss and should be an amount that you can afford without stuggle, don't go and bet your house on red. Once you reach your maximum loss you need to walk, and you should mentally prepare yourself for this outcome befor you start.
Don't take debit cards to the casino:
If you're playing at a land-based casino then beware, they have machines everywhere you turn... Everywhere. So leave your cards at home and only take enough money for a taxi ride home plus your maximum loss for the night, another good tip is to keep your taxi money in the other pocket otherwise you'll be walking home in the rain.
If you're playing roulette at a responsible online casino then they'll have an option somewhere which allows you to set a maximum deposit limit per day, and any change you make to this limit is only effective after 24 hours.
Remember:
Stay positive (don't cry about losing), don't gamble what you can't afford to lose, and set targets. Do this and you'll always be a winner, at-least mentally anyway.