I do carry everything with me on vacation (like my trip to Sweden this summer or the US and family this spring) because I just don't know what yarn I will come by. I love shopping yarn on the road and even took a small folder with patterns I wanted to go yarn hunting for. I was successfull, really.
If I take a daytrip on the train (for work but just stuck in the train, mostly) I take what I need (approx). Lately I wanted to make squares for my blanket, and 2 of them involved cables, 3 over 3. I did not bring a cable needle and there were a lot of cables. Well, I would have had emergency replacements (and if I go and ask the diner car for a straw, you know) but I just braved it and practiced my 3 over 3 without cable needle. They all came out beautiful and I only got myself in trouble once (dropping and not noticing eeeek)
A crochet hook usually goes into my bag (and gets stuck in the ball much too often) just for having a magic wand when you need one.
And, yeah, I can be pretty cought up in my knitting these days. But it does keep me relaxed, calm, more tolerant to long trips, awake, more happy, acomplished, warm, good looking, well dressed, liked for gifts and overall a better person. Which ONE hobby can really do all that (and not say Crochet, right now!)