There are positive and negative effects from trying to ‘outdo yourself’. On the one hand, it is a good thing to be trying to become better than you were yesterday—more knowledge, virtuous, skilled; a better person overall. Taken to an extreme, this can of course, be harmful; though this is a problem that doesn’t need much attention here, because miniscule is the number of people who suffer the detrimental effects of too much focus on betterment; and even so, this is still better than not caring about betterment.
But the middle-ground, here—the medium between not giving a damn, and being obsessive—presents a problem that absolutely warrants attention; this medium is likely where you, my dear reader, sit. The problem, quite simply, is the pressure, the internal and external expectations, of having to match previous achievements—be them award tallies, recognition, financial reward, personal satisfaction, and so forth. These expectations can distort perception, impair your focus, destroy your inspiration, hinder your happiness, confuse you, spoil your work. The driven person must be careful.
With time—as you mature, age, develop skills and have more experiences—you may look back on your former self, or work you did in the past, with an embarrassment, difficulty, and maybe even regret; in most cases, this is good, because it means that you have grown, that you have improved, and, that you will most likely never make the mistakes again.
On the other hand, you may look back on it as a burden, which can be crippling; this tends to happen if the phase of your life in question was a particularly blissful or very creative time, and you are worrying about your ability to top it, match it, or, that you haven’t improved, and maybe even got worse. This is a very common experience amongst creative artists and top performers—they feel compelled to match our ‘outdo’ themselves, or their own work, which can be daunting, confusing, immobilising.
The problem with this is twofold: firstly, worrying about the past like this is foolish; the past is done, cannot be changed, and fretting about it is a sorry waste of time, energy and morale; secondly, as long as the worrying continues, the produced work going forwards will very likely be sub-par—because it is produced with the wrong intentions. Whether the comparison is to your former self—your beliefs, ideas, energy, passion, skills, ability, etc—or a project you completed, at the time you did so you were very likely not thinking the same way you may now be (worrying about the past). But you were thinking about that very moment.
The problem is one of intentions; if you try to replicate this piece of work with the sole intention of trying to replicate it, if it was something special, then you will most likely fail and have a very miserable time in the process. If you instead focus on the task at hand, on your art, on this very moment, then you relieve yourself of a harmful burden, and granted that you have grown as a person since, will probably produce even better work—but you can’t know that NOW, and you shouldn’t’ try to.