I think that political leaders must assess the decisions that they plan to make carefully. Not only looking at the final goal in mind, but also how they will get to that goal. Who will be affected by it the most? Can this be compensated for? Do the benefits of achieving this goal outweigh the costs of it.
I think that political leaders who actually care about the people they are serving, do consider the costs of their decisions. One would hope, that at times, it is difficult for them, and that they go to bed at night thinking about the costs of that decision.
Other things to consider are the longer term goals. A policy might not be popular right now, or for the next few years or months it may have a terrible cost on people. But what benefit will it bring in a year, or 10 years? Speaking from my own country, the government has introduced several policies such as a Mining Tax and a Carbon Tax, that we will reap the benefits of moreso in the decades to come. Right now it's unpopular, but I think in a few more years, people will look back on it and say that it was a good decision.