One has to fight the evil inclination every day.  Sometimes it is a very difficult fight. If you think it is not worth the struggle , I'll remind you that the evil inclination  pushes one towards evil and tries to convince a person to do the lowest of things.

If you think it is difficult to fight the evil inclination , it is even more difficult to allow it to win. Once you concede to it , it is can pull you down further and further and take any good portion you may have.

You might say, I don’t have to fight the evil inclination because I only allow myself to be negative to a certain point and then I reverse my direction. In this way I stay on controlled plateau.

The Sages have stated clearly (and any cigarette smoker can testify to this) :

Mishna Yoma 8:9

One who says, "I will sin, and then repent, I will sin [again], and then repent," will not receive an opportunity to repent;

The only possibility is to fight the evil inclination , our negative tendencies, each day, in earnest.

Everything the negative inclination has to offer is false and of no true value anyway. (I get the following comparison from R Ronen Chaziza.)  An 18 year old student is about to embark on studies towards his dream career. He meets a cult leader who tempts him with a few nice words and convinces him to join his cult instead. The 18 year old now loses years , money , and who knows what else. He becomes subjugated to this cult leader, for the pittance of few flattering words.

The fight is worthwhile, for on this road you save yourself from many evils, you get a lot of wisdom, you discover potential in yourself , potential you may never have discovered, you become a better person !

It is not enough to say "from this day forth I will fight my negative tendencies".  Negative tendencies are strong, persistent and exert constant pressure on a person . Even if you take this decision with complete conviction,  you are likely to slip up later down the road.

The way to overcome ones negative inclinations is through daily Torah study.

The Talmud states:

Even so did the Holy One, blessed be He, speak unto Israel: ‘My children! I created the Evil Desire, but I [also] created the Torah, as its antidote; if you occupy yourselves with the Torah, you will not be delivered into his hand."

The way to overcome negative tendencies is to make a regimen of daily Torah study and not break it for anything in the world.