JeanneD4RK:
No decoupling capacitor one the breadboard, and it was working flawlessly.. I can try tho.
Very often things work just fine without those caps - especially in a quick test. But for long term use they're essential for stability, as you will at times have some stronger EMI (ranging from switching on/off electrical appliances such as heaters and washing machines to nearby thunderstorms) that make your processor hang or do unexpected things.
Placement of such caps is also important. C1 goes directly to the pins of your 433 MHz module. C2 should be placed as close as possible to the Vcc pin of your ATtiny. Each chip gets one such a cap (it's good practice to add multiple filtering caps for chips that have multiple Vcc pins, one for each pin) - even though they're on the same wire, the voltage on either end of the wire is not always the same, especially noise can be very different on two ends of a wire (which is very interesting to see - I've been playing with a cap placing at different places of my breadboard and checking the levels with a scope at different places along the rail - just moving it by 5-10 cm can make a HUGE difference).