What would you say if I said, "I just can't go without oxygen! I've met people who are still holding their breath at 12:00, but when I start holding my breath at 11:00, I just can't make it to 11:02, let alone 12:00. What can I do?"
I suggest you'd tell me not to be so silly (or something more colourful that means the same thing). The truth is, you need oxygen. You can't go without it for any length of time. That's just the way it is.
It is the same with sleep. If you need 7-8 hours then, well, that's what you need.
(If you regularly feel you need more than 8 hours sleep each night, you might consider a trip to the doctor. Various medical conditions can leave you very tired.)
Given that you need at least 7 hours, you can't expect to be able to go to bed late, go without naps and then get up early every day. It just doesn't work that way. People who claim to sleep only 4/5 hours every day are either (1) napping in the day (2) lying or (3) not normal (and not in a way that you get to choose).
So, your options are:
- Get to bed earlier
- Stop trying to get up earlier
- Take naps
If you still want to get up earlier, and are willing to make that work by getting to bed earlier, you could do something like this:
First, you need to make sure your bed time / rising time is consistent for a couple of weeks. During this phase, don't try to make your getting up time early. Just make sure that you have a regular bed time and a regular rising time every day, and that there are a good 8 hours between the two. Move your alarm clock / phone away from the bed so you can't hit snooze
Second, shift your bed time / rising time 5 minutes earlier. Maintain this pattern for 1 week.
Repeat step (2) until your getting-up time matches your target.
BTW: When you say, "I just can't wake up early", you're kidding yourself. You've confessed as much when you said, "I can force myself to wake up early is if I know that I've got to go somewhere". The problem is that you're either:
- Too tired
- Inconsistent, or
- You're trying to change too much too quickly
When you figure out which one, you can develop you own strategy for overcoming your difficulty.