In simple terms, achieving a goal has only three parts - the WHAT, the HOW and the DO.
The WHAT is the easy bit - in imagining the goal (lose weight, write a book, build a business) we are basically defining it; sure it might need a bit more detail, but that’s just adding flesh to the bones.
The HOW and DO are harder but there is a logical flow - you can DO before you know HOW but there’s a high chance of wasted effort, so it’s generally best to work out HOW before you DO, so that the DOing is just becomes a matter of effort and logistics.
The actual HOW will vary depending on the goal, and working out what needs to be done, and the skills that you will need is the most difficult bit - but knowing it’s the most difficult bit means it’s easy to know where to focus your effort.
Yes, achieving goals is simple, but as we all know, simple and easy are two very different things…