The particles へ and に in modern Japanese, when marking a destination, both mean "to", with the implication that the subject actually reaches the destination in question, so they are largely interchangeable in this usage. In pre-modern/Classical Japanese に implied that the subject reached the goal, but へ did not necessarily do so: in other words, へ could mean simply "towards", "in the direction of". That role has been taken on by the combination へと in Modern Japanese, so your sentence means "I feel that we have renounced/abandoned the happiness that we certainly had until forty years ago and are progressing in the direction of unhappiness, in the direction of unhappiness". It may be helpful to think of と as indicating the manner in which something is done, so へと would mean "as though to X". The repetition of 不幸な方へ suggests that the process is ineluctable, so I might go with "moving inevitably towards unhappiness", "advancing all the time towards unhappiness" or "moving ever closer towards unhappiness [although we haven't quite got there yet]". How to translate 放棄 also needs some thought. It suggests deliberately or consciously giving something up - for example, it's the word used in the Constitution for the renunciation of the use of military force.