Five things I learnt as a beginner about practicing taekwondo. Interestingly, the common theme is to detach myself from the outcome of my practice.
Have patience. Whether it is some technique which is frustrating you or dealing with training while injured, patience will see you through. I find that one tends to become discouraged and overwhelmed most because of a lack of willingness to savor the experience of learning a technique or working through injury. Sounds weird, but yes, looking back all the hard work put into learning a particular kick feels very satisfactory now. And it would have gone even more smoothly had I been patient with the learning process. Similarly, training through injury isn't as hopeless a task as it sounds like if you have the patience to believe that your body will heal even if mild stress is put on it.
To practice patience, one has to practice letting go of expectation. This doesn't mean that you lose all desire to improve. Instead, you practice putting yourself in an accepting frame of mind. Be an observer to your progress.
Keep at it. This one I never had much trouble with. I have never so far been low on motivation to go and attend class. (Now that I think of it however, in the great balanced-ness of all things, I have been low on motivation to get my other work done.)
In any case, there will be times when you are low on motivation, and you'll never regret pushing through your inertia. Since I have been practicing taekwondo, which, like any other activity requires a significant time commitment, I notice that I have become more laid-back about other time pressures. For example, I don't get overwhelmed anymore if I am a little late with school work because I got back late from class. In the great scheme of things, it doesn't matter. You'll stay up a few extra hours and get it done.
Relax. In class, I try to be focused and very relaxed at the same time. Extra tension serves no purpose, and I feel makes techniques harder to learn. Relaxation has to be both physical and mental. Mentally, don't put pressure on yourself, and keep thinking 'I better get it right this time'. Physically, don't tense up your body in anticipation to do a technique. I found this to be good to keep in mind while learning all the the various different, complicated and confusing ways that you lift your legs and move your torso to do wheel kicks, spinning stomp kicks, and spinning hook kicks.
Again, the way to achieve relaxation is to lose expectation, but not your focus. Focus is not that difficult to achieve, just empty your mind of thought about anything except what you are doing. The trick to relaxation is somehow not to focus too much.
No experience is wasted. Nothing that you learn is wasted. It may be that what you have learnt is not the most efficient way to defend yourself from an attacker. It may be that you learn something for a while, and then due to circumstances, have to take up some other martial art. It may be that you didn't learn from the 'best' teacher. Nevertheless, even that experience is something which is a part of your new personality, and is something more than not having learnt anything at all.
Practice. Both physically and in your mind. There is no substitute for lots of practice to perfect your technique. Keep in mind everything your teacher has pointed out to you during your practice, and try to perform your practice remembering these things.
Often, imagining yourself doing the thing which seems hard in real life physically helps overcome barriers. What I like to do is keep a mental video of somebody in my class who does the technique particularly well, and then 'photoshop' myself into the video, so that I see myself doing the technique with all the details in place.