Contraction of sounds is just another way of linking and blending of sounds to allow speed in speaking. There is nothing wrong with it, in fact, I personally think that this is helpful. But, contraction of sounds is only justifiable when you speak fast; otherwise, you will come across as being pretentious.
Spend your time and energy wisely by acquiring the most critical sounds in English. When you have overcome the most challenging sounds in English pronunciation, it will be a breeze for you to learn accessory sounds like contractions.