Fenrir Question

I've just finished all the Asgard stuff for Valhalla, and I'm confused about how much Havi accepts his fate or not. I guess this is a problem in any setting where 'fate' is always 100% accurate and people still try to mess with it... but my question is this: If Havi understands that he is to be killed by Fenrir during Ragnarok, then why is it so important that he binds Fenrir? He acknowledges Fenrir will still kill him, it's 100% going to happen, but he still goes through it all, costs Tyr his arm, and just ensures he has a pissed-off Fenrir to kill him instead of one that might kill him mercifully.