Everything has its consequences. Take a left turn rather than a right, for example, and the course of history shifts; say yes rather than no, or the reverse, and nothing will ever be the same. That goes for our ethical and mitzvah-based choices all the more so: each decision to do this rather than that has its worldly or other-worldly repercussions, some of which are dire. The point of the matter is that if I were to do something particularly wrong to someone else, not only would he be harmed in the process — I would be, too, and perhaps to an unimaginable degree.
That was the Mussar theme that R’ Salanter most especially dwelt upon, and the full understanding of its implications is termed Yirat HaOnesh — fearing the penalty that can come upon you if you harm someone (or go against G-d’s intentions on other levels).
In fact, he contended that the first and most fundamental thing anyone who hoped to achieve spiritual excellence would need is to take the repercussions of his misdeeds very, very seriously, and to worry about them. And R’ Salanter derived this from the frankly intimidating idea that each one of us is to be acutely aware of “where you’re heading (after death) and before Whom you’re to give an account and a reckoning” for all of your deeds in life (Pirkei Avot 3:1).
But most of us would definitely not like to focus on death and its aftermath. It’s too frightening and depressing. We’d rather concentrate on life and its beauty.
“The fact is, it’s kind of astonishing though that mankind doesn’t concentrate on acquiring this” — the fear of punishment, R’ Salanter is noted as having said, what with “all the calamities that force themselves onto the world that agitate the soul to its core, and which would be expected to fill one’s heart with dread” anyway, but which somehow don’t. We prefer to not concentrate on such things.
But R’ Salanter likened that to hiding under your pillows at the crack of thunder in the night and sticking your fingers in your ears, and imagining that that will save you from harm! But in fact there’s no escaping the fact that every action has its eternal and temporal consequences, and that each one of us is to consider the role we ourselves play in those we brought on to others, and those we ourselves will have to bear.
R’ Salanter made the point that some people shun Mussar study just to avoid these ideas. But he offered that that shouldn’t be so, since the fear of punishment doesn’t just come over you from the first: it takes years and concentrated Mussar study to come upon it, so you should study it for all the other good things you’ll derive from doing that. Secondly, you’ll be so absorbed in your study and captivated by the ideas you come upon there that you won’t belabor the point and won’t be saddened by it after all. And you’d also be so drawn by the notion of your fulfilling your personal potential as a human being and as a Jew that you’ll only want to go on with your studies.
Still and all, if you’d rather not concentrate on the above, then there’s a world of inspiring material in Mussar literature that would encourage you onward. You might want to concentrate instead on the bounteous reward due the righteous in the afterlife in contrast to what’s due the wrongful; or to focus on G-d’s benevolence, His caring for and His watching over us all the time, and so much more.