Why would my father take his own life after everything he went through?

because he could no longer live his life the way he enjoyed it and had accomplished more than he wanted and dreamed for... so it wouldnt be too hard to understand for me, because if i wasnt able to do the things i was meant for and believe was my purpose i would take it as a sign my part in this life is done... he wasnt sad, but knew there wasnt going to be as much understanding which is why he left the letter... he knew he could not go on living like that and would rather die not knowing what it would be like if he had too... very admirable choice in my eyes....