As you set up an over all goal and define smaller steps to get there, it is also a good idea to think about when you want to reach your over all goal.
Personally, I like to set a staring point from where I start counting my progress. This way I can tell how I am doing and choose to adjust my timeframe if I run into unexpected events. I, for one, tend to be a bit time optimistic, and tend to set the time to reach my end goal a little too hard to reach. But this can also work as a motivator to push myself and face the challenges. But we are all different and need different things to get us going, the most important thing in setting a timeframe for you is that it is realistic and obtainable, and that you are openminded and honest. Having to adjust your timeframe is not the same as failing to reach the goal. It is just adjusting your timeframe. Nothing more, nothing less.
Another important part in setting a timeframe is to actually give yourself time to accomplish your goal.
If we look at running example again. To reach the first step, run and walk 2 km, you need to start doing this. Say two to three times a week. And as you have stated this to yourself, you can also schedule time when you can do this. There is a huge difference in knowing that you will do something compared to when you will do something.
Let’s say you schedule your running-days to Monday, Wednesday and Saturday. Mondays at 18:30. Wednesdays at 17:00. And Saturdays at 09:00.
You create your own prerequisites to reach your goals. And you need to do everything you can to help you reach your goal and try to beat your own negative thoughts that may prevent you from claiming your dream. Accept the challenge and adapt it to you and do whatever changes you need to do to give yourself the opportunities to reach your goal.