Regret
If you try to put your soul into everything, you'll regret it. It's not so much that putting your soul into things is bad, but every single thing? You'll burn out immediately. You won't be able to be good at any of those things. And you'll regret all the time you wasted trying to be the best at everything.
Imagine if you went full force into everything you've ever even thought of doing. Imagine how burnt out your soul would be. Imagine all the regret you'd have that you didn't just stick to one thing and do it well.
かい
くや, く
None
The regret is too strong for you to ignore, so you decide to drop everything but kayaking (かい). If there's one thing you refuse to regret, it's your bright orange kayak and all the friends you made at kayaking club.
Throw everything you regret away. Only kayak from now on.