I will argue...it's the finish.
The lone exception is a sprint. But nothing in life is a sprint.
Now, I am not saying the start isn't important. It's the foundation for the finish. It's just not AS important as the finish.
A couple of real life examples...
My dad's life was turned upside down in his 50's. Divorce. Career change. Some real life challenges. But he settled into a nice groove for his last 30 years on this planet and died with very little regret. He was ready to go.
Recently I met an older couple at a restaurant. I would guess they were in their 80's. They were at the table next to us. I could see they were holding each other's hands throughout dinner, laughing and just really enjoying each other's company. I went over and asked them "what the occasion was." His response was "every day is an occasion with my lovely wife." I asked them how long they had been together and their response was 31 years. They said it took them awhile but they finally found their soulmate.
When I competed in triathlons and marathons, I had a rule; nobody passed me and I passed everyone I could see in the last mile. There was nothing more motivating than knowing I had more left in the tank and others had nothing left.
I am a huge football fan. Bleed Packer green and Badger red. It is much more important to be playing your best football towards the end of the season than it is at the beginning.
Again, don't misinterpret...the beginning is important but make your finish the best it can be.
At the end of the day...no regrets. And that happens because of the end.
In the play of life...you want standing ovations at the end...not people leaving early.