It can definitely cost you the game, Playing with money you cannot afford to lose, Puts you on the defensive, and it stays in your mind that really, you should not be playing that game. If you make a deposit of $50, then start buying in for $10 Your money is not going to last you long, and you will probably blow the lot in one session.
Poker is not a Money Cow! Nor a way to get rich quick! It is Hard work and needs a lot of Study to become a Profitable Player, Bankroll Management is even more important for beginners because you will lose, it's inevitable, You simply cannot win every game you buy into.
Finding your comfortable limits, and sticking to them, does not make you a Coward, It means you have common sense and can afford to lose now and again, without it costing you a Small fortune. Because you will lose more than you think.