"If I take out a loan to live it up for a year, but then have no way of paying it back, because I haven't invested the money into anything substantial did things really got better for me?"
Yes. Because those you spent it with must have, or you wouldn't have been able to buy anything with it. Therefore you caused things to happen that wouldn't otherwise have happened.
Debt is one of human's greatest inventions. It's what allows us to ensure that the underlying currency - human labour time - isn't wasted because there is no call to use it today.
Instead we have a currency - "here's a pig, owe me one" that causes a surplus to arise. Some people won't be able to fulfil that promise in which case it will, in advanced societies, be cancelled. That's what bankruptcy is for. The assets you used to secure the loan are then transferred to others. However the use of labour time in others to create the capacity to generate a surplus remains somewhere down the induced transaction chain.
Debt is the magic by which money is created on demand. That causes information to be transmitted down the supply chain that causes the capacity to make more to arise.
Which is why those societies that use debt are more advanced than those that chose to outlaw its use. They ended up with fewer days wasted in aggregate and more capacity to produce.
Most people fulfil their promises since it is inherent in human society to do right by others. And quite a lot of people like holding the assets that represent the debt as a status symbol of how well they have done - whether they can actually really call in those promises or not.