His fellow Scot Rabbie Burns put it more eloquently:
But Mousie, thou art no thy lane,
In proving foresight may be vain:
The best-laid schemes o’ mice an’ men,
Gang aft a-gley,
An’ lea’e us nought but grief an’ pain,
For promis’d joy.
Of course you must have a plan for your football team and devise the best distribution on the pitch of the players that you have available to maximise your performance both in attack and in defence, and we can all argue about the best formation of the players to achieve that after the event, and of course application and the desire to win are also crucial:
BUT a lot of what determines the outcome of any one game is often accidental or arbitrary.
Last night Klopp got lots right, Liverpool played superbly and were arguably the better team on the night, but two great players on the top of their game and some slices of good fortune for Barcelona overcame that. What Eddie calls small margins gave Barca a decisive victory, whereas if Salah and Mane had been as sharp and clinical as we know they can be, the result could have been completely different. Salah's shot that hit the post went clear of everyone instead of hitting the net as expected, whereas the Suarez shot that hit the bar rebounded cleanly directly towards the onrushing Messi. Neither Salah or Suarez had intended those outcomes, and their respective managers had no control over them at all, but they were decisive.
Because football is essentially a low-scoring game, it's the effect that these split second incidents and actions have on the outcome of matches despite all the organisation and preparation put into the teams that makes the beautiful game so fascinating.