I'm confused about what you mean by "little milk stream." Pictures!
I can say that from
my experience, the height at which you pour is by far the
least critical factor. Pouring up high is just for looking cool. Pouring close to the cup is necessary for marking the drink at the end.
I try to offer a lot of advice on latte art because I think it's really cool. My ideas, which I find myself stating a lot, may or may not be good ones. But, when my latte art starts looking "off" the factors I examine are:
Froth volume > how foamy the milk is; "how much volume did I add to the milk?"
Froth consistency > how smooth and incorporated the foam is; "did I get a good roll/swirl?"
Timing > when you add volume is important! "did I increase the volume while the milk was still cool? did I steam too slow, or did I steam way too aggressively?"
I bet you're having a problem with one the first two. If the milk will only let you form a blob vaguely resembling a christmas tree, then you need to add less volume to make it more pourable. (For example when I shoot for a cappuccino froth consistency
**, hearts are the only thing I can pour.) If the milk only marks the latte at the last second and can't be shaped well, then the consistency is off and foam is just dumping out at the very end of your pour.
After managing the first two perfectly, my best pours occur when I add foam early in the steaming, but don't force huge amounts of air into the milk too quickly. It's a balance that I still don't understand, but milk does form microfoam the best while still cool.
**A cappuccino might not be the best example since the term is ever evolving. When I make a cappuccino, I want a lot of silky, light froth that sticks to my upper lip and coats my tongue on the first sip. I try to get 3/4" of standing foam after it has settled in my clear cups. My lattes are only defined by the amount of foam that gives me the best art.