In maseches taanis where the gemara tells us “mishenichnas adar marbin b’simcha”, rashi says that the increase in simcha is due to the miracles of purim and pesach. Clearly, the simcha does not end before pesach.
And even after Pesach just 2 weeks later the radiance of Geuloh continues with Yom ha’Atzma’ut.
Then 23 days later, the radiance of Simcha & Geuloh continues with Yom Yerusholayim.
Then 1 week later, Mattan Torah:- What greater Simchah!!! Ad haYom HaZeh, everyone talks about “Cheese & Wine Party”. This is exactly what we consume on Shovu’os as we celebrate Matan Torah.
Thereafter, I agree with you popa_bar_abba, that it is all down hill with Tammuz 17 thru Tisho b’Ov.
But just 6 days later it is Hag haMecholos [A.K.A. Chamisho Ossor b’Ov], unofficial early prelude to Ellul & Joy of Tekias Shofar.
Only time we talk about bitterness is via a vis MarCheshvan, and this is basically predicated on the anti Climax after so much joy with so many Yomim Tovim in Tishri, eventhough no specific Availus in MarCheshvon.