RNG is RNG, bad rolls can and will happen. Randomness also means that you aren't gaurenteed to get a high roll after a certain amount of low rolls, and vice versa, it is completely possible to get a string of very good rolls.

Only advice is to never leave until after what you are rolling for has been awarded. Sometimes your low roll still ends up winning (Gotta love beating a person's 5 with a 6!)