When you're feeling un-inspired or are out of practice, one thing you can try is what I call 'abstract doodling'. To do this, start at any point, making lines, shapes, textures. Don't draw identifiable objects. You can draw forms with shading and textures, but keep them vague. This takes the pressure off you to draw 'correctly' or over-focus on trying to get something 'right', and helps you to switch into a meditative mindset. Although these doodles make look very intricate and even composed, they're very 'organic' creations - I start at a random point and expand out; there's no plan or theme. Your abstract doodles will probably look very different then mine; it's a very personal process. The goal is not to create a beautiful work of art (although that might happen), but to ease you into a 'flow state' so you'll feel calmer and more confident at drawing. I personally find it much easier to problem solve in a calm, relaxed state - and much of art is visual problem solving. I usually use either ballpoint pen or microns for this process, because you can't erase the marks and therefore have to commit to building on what you put down (instead of trying to 'perfect' your image), but you can use any material you're comfortable with. Sometimes I end up doodling more identifiable shapes - this usually happens after I do a few abstract doodles and feel like being a little more ambitious, or if the doodling is inspired by a specific subject or theme. But even here, I try not to control the process too much - if it flows easily, go for it, but if not, just let it become whatever comes most naturally to you.