What are your favorite dramas with lots of pining?

Plenty of pining in these cross-dressing dramas where the FL has to pretend to be a boy:

• Coffee Prince - The beach scene killed me. In a good way.
  
• Bromance - Everything you're looking for. 
• Love in the Moonlight - They face multiple obstacles, so even when they get past one obstacle and are together / not pining for a while, there are other obstacles that cause more pining later.
• Sungkyunkwan Scandal - In addition to the leads, Yoo Ah In's character has some great pining scenes and it's implied that Song Joong Ki's character also does some pining in his own way.

Also:

• Crash Landing on You - It's not really a situation where they can't confess / don't know how the other person feels. They both sense it and indirectly acknowledge those feelings fairly early on, but they know they can't be together. Even when they give in to their feelings, they still have to separate, which makes for more pining.
• Healer - The pining happens because the ML can't directly reveal his secret identity to the FL or bring her into his real life because he fears it would put her in danger. So even after the leads have kissed (the FL's eyes were covered) and generally understand how they both feel, there's still pining. 
• My Secret Romance - This one is pretty light and also an unusual take. They had a one-night stand the first time they met, but out of fear of embarrassment they misunderstand each other when they meet again, which leads to some entertaining antics but also some good pining.
• The Imperial Doctress - You have to be very, very patient, but they do end up with each other in the very end.
• In Time With You - The ML's feelings are one-sided for a long time. Love the pining in this one.
• Lost Love in Times - At first it may seem like there isn't much pining involved in the leads' romance, but a few episodes in there's a big shift that changes the dynamic.

Piece of your mind- It's not usual ROM COM, its more on beautiful ascept of love and life, it's the perfect theme of unrequited love/crush as whole drama follows the plot, but with a happy ending and a genuine feelings and confession. 

 You just fall in love with every character.

I've seen many many dramas that fit your requirements, but I don't want to make it confusing for you by adding even those dramas here. Because out of all those drama, I think I picked the right one for you. I really hope you'll like my pick.