You don’t have to love everything in life. But it’s useful and helpful if you can explain why you don’t like it, and it gives you more credibility. To pass something off as ‘rubbish’, or ‘boring’, ‘lame’, ‘pointless’ or ‘wrong’, isn’t necessarily helpful to those in question if you have no reasoning behind it.
This is broad and could cover a vast range of situations, so bear that in mind.
If you ever are going to criticise something, be it a piece of theatre, a niggle in a relationship, something you brought from a shop or your friend’s English essay – then that’s fine. Criticism helps us to get better, to be better. But only when it’s constructive. It’s always important that you can explain WHY it was rubbish, boring, lame, pointless or wrong, and perhaps even offer your own alternative. They don’t have to take it, but at least you’ve opened a window where you’ve closed a door. If you can’t do that, then I wouldn’t say anything, as unconstructive criticism is pointless, unhelpful and can make others feel a bit lost.
This rule applies to you too. Demand constructive criticism from others, in your work, life and relationships. Refuse any form of criticism, unless it’s constructive. If it seems like a shallow / superficial criticism, demand more information, explaining that you can only begin to address it if you have all of the details. And if none can be offered, then perhaps there is another reason for that person’s criticism in the first place, which is not primarily you. They may be criticising because they feel insecure, or it makes them feel better about their own stuff as they push somebody else down. Make sure you get the maximum amount of use from all criticism you receive – it’s not always a bad thing, it can be very helpful.
Also, you are allowed to take nearly all criticism with a pinch of salt. It’s mostly just opinion anyway.