The advantages of killing myself outweigh the advantages of staying alive

[Marktheghost]

So, after 23 years of knowing that I want to kill myself, now I’ve finally got the chance to do it, why am I feeling unsure about it?

 

[WornOutLife]

Because of your survival instinct. It's hard to beat that as*hole.

 

[rs929]

I don't necessarily agree with this. SI kicks in when you're just about to do it, like when you're contemplating the floor from 20 stories above, or grasping for air while doing partial, or when you know there's no turning back after ingesting that SN. Instinct kicks in when you're about to execute it.
But OP is in the planning stage. Maybe he is actually having second thoughts.

 

[Meditation guide]

SI kicks in when you're just about to do it,

I think it's a lot more devious and cunning that that. I think it's operating in the background at all times, at least in my case.
I know I should ctb immediately and yet I don't, I keep finding things to enjoy, really small pitiful things, a new food, a new movie, things that shouldn't stop me.

 

[KleinerWolf]

I think it's hard to let go if you even have a tiny bit of hope or something to work with.

Also, no one wants to die.
There's something to do with non-existence and potential regrets in life that people still hold onto.

 

[sadworld]

Killing yourself goes against all of your human instincts, that's why.

 

[Nymph]

Survival instinct

 

[L I F E T O L O S E]

fear to die.
u probably haven't died inside yet

 

[Wraith]

Perhaps it's the fear of the unknown or even of failure, but survival instinct is undoubtedly a factor. Humans have mental SI along with physical SI, and hope is among the strongest of mental SI. I think many of us fight with hope.

 

[TAW122]

This is because of your survival instinct, like @WornOutLife said. In addition to this, I believe you may have things that you feel like you have to do or want to do before you CTB, which may be an extension of the SI but not necessarily.