If you think that you are too tired to workout then you cannot afford NOT to workout!
Feeling too tired is not an excuse to skip today's workout. Sure, feel free to alter the type of exericise you do and perhaps even the amount of time you spend doing it. Just do it. Do that and you'll thank me. Do 20, 30 or 45+ minutes of exercise and that will turn a lacklustre day that is into one that is massively positive and full of energy! 
Instead of feeling like "pooped" (like fat cat above) you'll be "popping" with energy (like crazy cat below) and feel good about yourself because you're a person who keeps their promises to themselves and follows through! 
