This is really just a matter of maturity and discipline. The OP is unable to say "No" to themself. Having discipline is being able to power through the boring stuff because you know it's important.
OP does not need ADD drugs, all they need to do is commit to finishing a task, and not to pick up anything new until the current task is completed, no matter how "fun" the other tasks seem.
OP does not need ADD drugs, all they need to do is commit to finishing a task, and not to pick up anything new until the current task is completed, no matter how "fun" the other tasks seem.