[Big A]

You are right that giving oneself as a sacrifice to God has in several mythologies figured to be the final phase of an intense desire to see Him/Her. Why, even Sri Ramakrishna Paramahansa did that. But that is quite different from what suicide would mean in todays world, isn't it?

Love and Light.

[Fegasderty]

this world is nothing but a great illusion , and one comes to truly accept and realise this , this body becomes nothing more than a hinderance to the soul. sri ramakrishna had reached a state of samadee where the soul just gave up the body. this is not suicide !
this is like a young coconut plant shedding its husk . since the body cannot be seen as real , the shedding of the body is just a stage in spiritual growth.

[Paul Bunyan]

Is giving up body equal to suicide? Was it not considered sin?

Tamil puram poetry exalts several types of ritual suicide committed by warriors. Vadakkirutthal, avippali, marakkanchi... you'll find all these celebrated and glorified in our classical literature. For Tamils, at least, suicide being considered sinful is a relatively recent development. Suicide as a form of cowardice is a different issue, but that's not what we're talking about.

Hinduism, too, takes a more nuanced view of suicide. The law books condemn suicide generally as sinful, but literature suggests there were exceptional circumstances where it wasn't a sin. The uttararamayana for example talks of Rama ending his life by ritually drowning himself in the Sarayu. Whatever you think of the validity of the Uttararamayana, they're hardly likely to have depicted him doing that if suicide was considered sinful. Then there's "sati" itself, which was considered a glorious act in its time. Jainism has "sallekhana" as a permitted form of suicide in some circumstances. And so on.