One problem area that I see with so many students learning to improvise is this...they lose their place in the song during their solo.
With so much focus placed on note choice, it's easy to lose your place in the bar ("where's 1?") and the form ("when do I stop?").
For a long time I struggled with this issue (still do learning new/difficult tunes). Thankfully, I learned a practice tip that fixes the problem of getting lost in the form.
Alternate bars of comping and soloing.
Start by playing one measure of rhythm guitar followed by one measure of soloing. Do that for an entire chorus. This develops 2 important areas of your musicianship. One, you'll develop an internal sense for beat one. Two, you'll be forced to really learn the changes of whatever tune you're practicing.
Once you've gotten comfortable switching between rhythm and lead every bar, try alternating every 2 bars. Then try alternating every 4 bars.
As is often the case, the concept is simple, but actually doing it can be tricky. Start out with a simple tune (maybe a 12 bar blues) and be patient.
It won't be long before you see huge results in your sense of time, knowledge of the changes, and mastery of the forms.
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