Fighting to Make the World Better by Bettering Ourselves
Everyone's actions play a part in the world. The RaMBa"M (Maimonides) writes that each person's actions are weighed in to the larger whole, such that the performance of a mitzvah or any good act which is in line with The Torah, such as bettering ourselves and our middos (character traits), can tip the balance of the person such that the person's good outweighs his bad and he is judged favorably by HaShem as a result, among other things. The RaMBa"M recommends that the person view each action as having the great significance of tipping the balance in favor of the person's good outweighing his bad actions. This is not only limited to the person, for it is up to us to view each of our actions as having the potential of leading to a good judgment for an entire city, country, and even for the entire world. If one seriously views each action he performs as having such a serious consequence, both favorably, and, chas v'shalom, unfavorably, he will make all the greater effort to improve himself through improving his character traits and taking advantage of opportunities to perform mitzvos. On the other hand, if the person feels the inclination to sin or allow his yetzer HaRa (evil inclination) to "get the better of him", he should determine to simply not give in to this inclination so as to avoid the potential negative consequences that he may experience, as well as the punishment that he has the power to cause to be averted from a city, country, as well as the entire world.
By Overcoming the Yetzer HaRa, we Benefit, By Giving in, We Lose
The Yetzer HaRa has no power to compel us to perform that which is evil, but rather encourages us to give in to our negative inclination, thereby losing the battle to him. HaShem tells Kayin, "...'Why are you angry and why are you downcast. Isn't it that if you improve yourself you will be forgiven, and if you do not improve, sin crouches at the opening, and it's desire is to you, and you shall rule over it.'" (B'reishis: 4; 6 - 7) Instead of listening to HaShem's advice, by which he would have been spared of the great sin of murdering his brother, Hevel, Kayin failed and actively became subservient to the inclination of his Yetzer HaRa. (4; 8) As we learn from the above, HaShem is telling each person, not just Kayin, that we are Created to rule over our evil inclination. We also see that prior to Kayin's grevious sin, he was angry and downcast. These two attributes, among others, have the great ability to lead to a person who has the potential for great good, as was the case with Kayin - the first human that was born - to come to perform such a great sin. Of course, Kayin did regret his sin and performed teshuvah (repentance) (B'reishis: 4; 13 - 14), which allowed for the punishment to be limited to exile and he did live a long life before being killed. We can use the Yetzer HaRa for our benefit by standing up to him, and we will always overcome him, B'Ezras HaShem. By overcoming the Yetzer HaRa, we serve to strengthen ourselves spiritually and benefit ourselves in The World to Come and in this world. We also increase our connection to HaShem and our spiritual level. However, in contrast, if we allow ourselves to "give in" and perform the sin, thereby gaining very limited pleasure in exchange for great loss, chas v'shalom, we have failed that battle against the Yetzer HaRa - the battle against he who is described in the gemara as the one who hates us.
Always Remember HaShem and Don't Allow Yourself to Sin
One of the pieces of advice given in "Pirkei Avos" to the person such that he won't sin is that he should always recognize that all of his actions are 1) watched by HaShem, 2) Heard by HaShem, and 3) Recorded by HaShem. It is only when we allow HaShem to be distant from our hearts, forgetting HaShem is watching our every action, or, at the very least, allowing ourselves to not focus on this fact, which provides the Yetzer HaRa the perfect opportunity to try to encourage us to sin. By distancing HaShem from our thoughts, even for one moment, we put ourselves at greater danger of deciding to follow the Yetzer HaRa instead of the mitzvos of HaShem, chas v'shalom.
"Sha'arei Teshuvah" - Remember HaShem, Fear Him at Least as Much as you
In "Sha'arei Teshuvah" of Rabbeinu Yonah, we learn that we should fear HaShem no less than we do people. If the person would not sin if a person would sin him, he shouldn't sin ever, for HaShem sees him. This was the blessing that Rabbi Yochanan ben Zakkai gave to his students immediately prior to his passing. (B'rachos, 28b) We should be determine to better ourselves and always recognized that HaShem is watching - "שויתי ה לנגדי תמיד" - "I constantly place HaShem before me". Once we truly do this, we will not fall to sin. May we all merit to have true fear of HaShem.
שויתי י-ה-ו-ה לנגדי תמיד