When i can leave ??

It is such as four years who i am a employee of this company, i feel so happy to complete this position in the first time, but now i feel so boring and much want to leave from this job, why am i like this ?? who know the reason?? i don't know how long i can stay here, as now am much boring and hate here so much  .who know the place looking for staff ?? i want to leave from this job so much