A few thoughts for you to consider adding to your self-teaching repertoire:

1.  Always try three times (no matter what the task)... If you have succeeded by your third try, then take a break or move on to something else for the time being... You'll often succeed at your next session (or the following one), but if you keep pushing after three tries you may be tensing up and/or causing yourself injury... So try three times, then give it a rest.

2. Record your practice sessions, and listen to them as if they were being played by a student (this isn't always necessary, but can give you some real insights if done, say, once a month or so)... Write down your observations and look at them in a day or two--- BUT make sure that your comments are phrased positively (as in First attack in the third movement needs to be clearer NOT first attack in the third movement STUNK!), and that you actively think about the best way to correct any mistakes (ie: Practice air attacks, then marcato, set the tongue before releasing air...be as specific as you can)

3. Take some time every day for visualization:  SEE yourself succeeding at your goals (See yourself performing confidently in front of an audience, See yourself confidently playing that technical passage in your solo, Hear your clear tone and clean attacks)

4. Listen to (and imitate) great artists, both on yourr instrrument and on other instruments (including voice).... Analyze what makes their performances seem so effortless, so musical.... How do they phrase?  How do they connect their phrases?  How do they release notes? Practice imitating those phrases, releases, etc...

5. Take a few minutes to do some deep breathing before you play.