Of course, we know nothing about Yaakov and Eisav, but Chazal say: פִּּקּוּדֵי ה' יְשָׁרִּים מְשַׁמְּחֵי לֵב (תהלים יט ט) learning Torah makes you happy; certainly, Yaakov Avinu, the יֹשֵׁב אֹהָלִּים, big Masmid was full of Simcha. And Eisav who is described as an Adam Battel (Rashi) who wasted his time on capturing animals (i.e. doing nothing constructive) couldn’t really be a truly happy person. Fake fun brings no Simcha.
Sometimes Simcha Is Virtually Your Only Mitzva
When dealing with the public, many, many times I see a lack of Simcha. People want to be נוֹשֵׂא בְּעוֹל (feel the plight) with the soldiers in Eretz Yisroel. However, they end up getting depressed, or sleeping “2 ½ hours at night” (unquote). They worry about their sins, and the average person has loads of guilt. There are no rules, and people are different. But it has happened that I’ve told people: “You have only one Mitzva; be B'simcha!”
Of course, they have to keep Taryag Mitzvos. But they need a main focus of Simcha to dominate their lives, or else they could be in big trouble. And despite their “Shas”, and loads of Tzedaka and Chesed and Dikduk B’mitzvos, they are nervous and/or angry and/or depressive. Some of them need desperately to practice Simcha, even בֵּין הַפְּרָקִּים during the breaks while reading Eicha on Tisha B’av, on the holy day of Yom Kippur, and even to squeeze in some Simcha energy while they have a blatt Gemara open before them.