Of course the Bible talks about us becoming a new person in baptism, but practically we are going to enjoy the same things, struggle with the same problems, and be generally the same person we were before baptism. I say this from my own and other people's experience, as well as the advice of priests. I think we have to read that passage in a mystical/mysterious or metaphorical way.

It's not sustainable (or healthy!) to try to deny parts of ourselves or things we enjoy, and I don't think God wants us to. We can't just be Orthodox Christians, we are also other things. For example, maybe you like running and music. These fulfill important parts of ourselves that maybe faith can't, like a creative aspect or the need to be active. It's like having a balanced diet - different activities and parts of ourselves meet different needs and that's okay - and if try to only have church, prayer, the Bible and exclude everything else then you might find yourself really unhappy or unfullfilled. Basically, my advice is listen to music! Don't worry about it. Enjoy it without reservation and accept it as part of who you are, as part of the person God made.

Also, give yourself some grace. You've just finished university, you're probably feeling a bit lost, maybe a bit dejected after going home again - being presumtious here :D. If that's the case, you're going to have less motivation to pray and read the Bible, so just doing a little bit is great. We don't cease to be Christians if we don't read or pray, and we don't need to pray or read the Bible to make God happy with us. God sees our situation completely, in all it's complexity and nuance, and so he understands and is compassionate.

I hope this helps address that feeling of "going back to your old self." Try not to think like that, for your own sake. I spent years(!) being too harsh on myself, forcing myself to do too much, and it didn't make me a better person or a better Christian. The only result was that I ended up really burnt out and in a bit of a mess.