In English, the phrase is "I had my heart set on it". It's not quite right to say that thinking, wishing, etc are done solely by the brain. We are "feeling" creatures too. A lot of the emotions are managed by the release of hormones, which alter our bodies (all of our body, not just the brain) in different ways. So maybe "heart" is another word for "hormones"? When you REALLY want something, you MUST get your emotions involved and get yourself PASSIONATE about what it is you want. This is especially true if it is something difficult, like stopping smoking, losing weight, gaining additional educational qualifications, writing a great novel, becoming the best parent possible to your child, etc. In all of these, if you do not have your heart and emotions involved, you will not achieve them. The brain alone saying "I must lose weight", etc, will not do it. Put your heart into it and it's a lot easier.