One way or another, we are here to work. Our sages say "adam le'amal yulad" - "a man was born to toil". There's no escaping it, and there are no two ways about it. As the Torah makes clear many times, and as we remember all the more so during the three weeks, if the Jewish people try to shirk their obligations to serve G-d through joy, they will serve their enemies through suffering instead. And as it is on a national level, so it applies on an individual level. Each one of us has his or her job to do. If we decide that it is too difficult to fight our evil inclinations, we will find ourselves fighting much more difficult and bitter things down the line, G-d forbid. One who gives up on his fight with the yetzer hara may find himself fighting his wife, fighting poverty, fighting illness, or any combination of these.
This world is like a hallway to the next. It is only a means to the ultimate goal of "Lachazos Be'noam Hashem" - to bask in the glory of G-d. The Kabbalistic books write that every Jew will have to come to his Tikkun (rectification) by hook or by crook. So why do it through many reincarnations and so much suffering, when we can much more easily serve G-d with happiness and accept the yoke of heaven with joy?
So next time the Yetzer Hara comes to you, tell him that you don't have a choice whether to work or not. Because in any event, somewhere down the line - you will have to do the work you were given. So instead of making it hard on yourself, do it the right way, the first time, with joy!