I haven't played music in quite a long time. Once thing I've noticed when I started playing again is that my tempo is completely horrible. When I play along to any song or instrumental, sometimes I play too fast, sometimes too slow, but never at the right tempo. Even when I'm not playing along to an existing recording, it's painfully obvious that my tempo is way too shaky. My awareness of this issue only makes things worse, because I get nervous and drift further away from the right tempo.

Tapping my foot doesn't help. I tap my foot at an equally wrong tempo.

Paying special attention to the drums doesn't help either. If I do, I can't concentrate on my own part.

Using a metronome only has the demoralizing effect of making me want to turn it off.

Is there any set of exercises and/or training guidelines specifically for practicing my tempo?