I'd also add:

• there's heaps of stuff that's 'useful'. what matters is how useful it is - especially in relation to things that might be more useful. we all have limited time and (other) resources. it's a cost/benefit ratio. the good is the enemy of the great, and all that.

• often it's unclear how useful something really is, you have to take this into account when you judge whether it's worth your while. and you also have to make a judgement about whether it's even worth your while to try evaluating it... coz there's always heaps and heaps of options and you can't spend your time evaluating them all.