Well, it's dependent on your style. Every play has developed his/her style based off their abilities at the game. Many people space, because of their style. My Yoshi, yes I'm using my Yoshi as an example on the ZSS boards, is one of the most aggressive things you will meet. I do not shield I do not space, I am in your face at all time, if I wish to block something I nair, or jab. You see you can use these tactics instead, which sets you apart from others. IMHO, spacing is a great thing to apply. But still you have to stay true to your style. Which is like my Yoshi, from what you are describing. What I would suggest is that you experiment in your friendlies with spacing, and then with your aggression. But keep in mind there can be a balance between the to. So don't go all agression and end up walking into an Fsmash.