Rather than "كن سعيداً بانتصارك" it should be "لقد انتصرت لسعادتك".
desistindo = "الاستسلام" not "اليأس"
Kindly edit your text to convey the accurate meaning.
Thanx.
OK...I get your point.
When I deal with these texts I ask the experts here in the site.
The bridge I was given for this text said: "for your happiness, you won". And I trust our experts since they are native speakers of the language.
So, to me it could possibly mean what you said.
But I was thinking the other way around. That he was fighting to get "happiness" and then he won it!! I hope I haven't strayed from the original.
So I was trying to find something that satisfies all possibilities. We can also try: "لسعادتك انتصرت ".
As for giving up, the reason I thought about "الاستسلام" was due to the concept of winning/losing which indicated an air of "battle".