Do you tend to overpack when you go on a trip? If you answered “yes”, then you're not alone. Many people pack things they end up not needing. This is mostly due to a lack of planning and travel anxiety.
It is easy to end up packing a ton of clothes you don't need when you have no idea what the weather at your destination will be like. This is why you should look up the average temperature for your destination, as well as the forecast for the time you will be there. This will help narrow down things you certainly won't need. Why pack a parka when it's going to be 60 degrees?
After you decide what you absolutely will and will not need for your trip, the next step is figuring out the best way to put it all in your suitcase. Make sure you start with all clean clothes, so do a load of laundry before you get packing. Next, decide how many of each thing you will need depending on how long your stay is. If your stay is only for a weekend, it is highly unlikely that you will need 10 pairs of underwear. To save on space in your bag, pack one pair of underwear/socks for each day you will be there.
It's tempting to pack way more than you need for the “just in case” habit but think about all the other trips you've taken and what you actually ended up using. Ultimately, it will save you space in your bag (and possibly money if you're flying on a plane) which could help you stick to your budget.