The key is to balance the ingredients. The trick to mixing difficult ingredients ( for example, vegetables and anything fibrous, hard, frozen or skinned ) is to mix in stages instead of putting everything in at the same time. Make sure you use enough liquid to prevent ingredients from weighing down and leave some room at the top to prevent it from overflowing. Drinking smoothies at  the morning help you to have a positive and energetic day ;)
Prepare the liquid base ( milk, yogurt ) and add the hard ingredients one by one ( vegetables, bananas), mixing between stockings. Then add all the other ingredients and beat until you get a creamy and homogeneous mixture.