What they have done now is combined that into one policy. Which is small. So, how does it really matter to you? Not much, actually. Most people won’t even notice it.
For the most part, this will help improve Google’s services. Now, you will be identified on all Google services as one user. And the information Google collects from one service, might be used for improving another services. For ex. if you specify a language preference in Google search, it will also be applied when you use YouTube.
This also means that your YouTube account might me linked with your public Google+ account. Also, Google can now serve you ads based on your behaviour on another service. So, the ads you get in Gmail will not necessarily be due to the content of your email, but related to a video you watched on YouTube. Maybe. Which is a good thing. If you have to see ads, why not see ads that are more relevant to you?
The important thing is, this is not going to affect you in a bad way. So, stop freaking out, and go back to what you were doing.
In case the above did not help you calm down, you can always delete your history across Google’ services. Google Search and YouTube maintain a history of what you searched for and what you watched, if you used these services while logged in. You can find these in the settings and delete them, and turn history off, so that Google will stop freaking you out.
BTW, here’s the link to the video in the image above! Back to business.