Why do people use drugs in bad periods in their lives, while using it results in even worse situations?

Because when we're feeling pain we'd rather daze out so we no longer have to "feel" except you only come back 10x more hurt and emotional than you would've doing it the sober/ strong way.

Drugs almost always release dopamine; that is fancy talk for something that makes someone feel good. Think of it as if you've won the lottery; it is comparable to some degree. Because it gives them those feelings, it provides some temporary respite.

Addiction is doing the same thing over and over in spite of negative consequences. The drugs are ones way of escaping their pain

When people are unable to regulate their emotions the nervous system goes into overdrive. Drugs are used as a way to self regulate when the individual perceives there is no other healthy options available. It gives them 'time off' their situation or problem and unfortunately after a short while the physcial addiction to the substance takes over and they are not able to regulate their daily like functions without it. As tolerance increases so does the amount required to achieve the inital effects. Unfortunately rehab is often the first time anyone assists them with their underlying mental health issues and show them a viable way of existance without substances. Although sadly not everyone makes it that far.