Maria, 
I understand you question and where you are coming from. there is a quote out there that says "I never said it would be easy, I only said it would be worth it". We keep those rules (commandments) because we believe: 
1. God has commanded them of us 
2. God will bless us if we keep them 
3. After trying God's promise to keep a commandment, we see that he does bless us immensely with happiness. Because we have tried this out for ourselves and know that it works, we will want to obey all of his commandments. 
 
I have found that I have more liberty and freedom by obeying those commandments, rather than viewing them as restrictions. No dating until 16 - I didn't have to worry about the pressures that come with having a girlfriend...and I definitely saved some money! No sex before marriage - I never had to worry about dealing with an unwanted pregnancy or sexual diseases. No coffee or caffeine - I didn't have to worry about my brain being taken over by short bursts of energy that always have a downtime waiting on the other end....plus I didn't have to ever worry about becoming addicted and having to spend $5 a day at Starbucks just to feel like I could start my day. 
 
Hope this helps