It really depends on the robustness of every piece of the chain, from Netflix all the way to your television. Netflix, itself, could be having problems that day, and that will cause issues. Or the problem could be general Internet network congestion (VERY unlikely). Or it could be that your Internet service provider's "pipes" are too small, and are overloaded at a certain point in time. Or it could be that your own home local area network is congested, or doesn't have the capacity to deliver a reliable video stream. And so on.
A few things I've done, that are within my control, to facilitate Internet streaming to my television:
First, I use a wired connection, all the way; no wireless. You could have the fastest wireless connections available (802.11n), but if your neighbor does as well, then you're going to get wireless collisions and that will drastically slow your wireless throughput. Nothing can interfere with the transmission going through your wires, except other things that
you are doing.
Second, I've upgraded my Internet connection from the standard service, to a service more amenable to high-speed downloading. Just taking Comcast as an example; this is how they sell their high-speed Internet service:
Performance: 12 Mbps/ 2 Mbps
Blast!®: 16 Mbps/ 2 Mbps
Ultra: 22 Mbps/ 5 Mbps
Extreme 50: 50 Mbps/ 10 Mbps
(The first number is the peak download speed; the second number is the peak upload speed. For streaming of television, you really just care about the first number.)
There should be no surprise that each level of service cost more than the previous. I upgraded to Blast! (and then later, when I switched to FiOS, selected their 25/15 plan).
Note that all of it was for naught, though. None of the streaming services provide
anything we want to watch closed captioned, and my wife is hearing impaired. This is a case where technology has outrun the ability for our government to protect the rights of protected classes, so the hearing impaired are currently, and shall for the foreseeable future, be treated as second-class citizens, as more and more of America starts getting their television entertainment via the Internet. So my family waits for industry and/or government to catch up with the latest developments of technology.