during world war 2 a German solider was captured by the Russians. he later escaped his captures and and started back to Germany. The solider had to cross some of Russia's coldest, harshest, terrain. The solider did end up making it back to Germany. now why am i telling you this... well the German knew that he had to cross a lot of land. it was plain out demoralizing to think of it like that. so the goal of get to Germany was replaced. the solider had 6 bullets. he kept all 6 in one hand. and every time he took 5,000 steps he would take one bullet from his right hand and move it to his left hand. and after they where all in his left hand he would do the same thing but bring it to his right hand. after some time (don't remember exact number, its an old story) he did finally get home.
once again... why am i telling you this? Well, getting a 99 in almost anything seems daunting. matter of fact once you get to lvl 90 you are only half way there! the moral of the story was that you need to cut the big goal into more manageable goals. example being into 1 lvl at a time. or even when 1 lvl equals 1m+ xp. set you goal 100k xp at a time. that way you don't feel like you are fighting a lost cause.