Have you ever undergone (by your choice or by fate) a significant life transformation for the good?

You don’t have to “out” yourself on the type of transformation, but if you have ever lost a lot of weight or gotten clean/sober, quit smoking or had any other significant transition for your betterment, what were the catalysts for this change? How long did it take the change to manifest? What did you do to keep yourself going during the hard days? Any advice?